diff --git a/CMakeLists.txt b/CMakeLists.txt
index c0ce129dfc..a4be4d6041 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,13 +39,17 @@ source_group(apps\\openmw\\mwinput FILES ${GAMEINPUT} ${GAMEINPUT_HEADER})
 
 set(GAMESCRIPT
     apps/openmw/mwscript/scriptmanager.cpp
-    apps/openmw/mwscript/interpretercontext.cpp)
+    apps/openmw/mwscript/interpretercontext.cpp
+    apps/openmw/mwscript/cellextensions.cpp
+    apps/openmw/mwscript/extensions.cpp)
 set(GAMESCRIPT_HEADER 
     apps/openmw/mwscript/locals.hpp
     apps/openmw/mwscript/scriptmanager.hpp
     apps/openmw/mwscript/compilercontext.hpp
     apps/openmw/mwscript/compilercontextscript.hpp
-    apps/openmw/mwscript/interpretercontext.hpp)
+    apps/openmw/mwscript/interpretercontext.hpp
+    apps/openmw/mwscript/cellextensions.hpp
+    apps/openmw/mwscript/extensions.hpp)
 source_group(apps\\openmw\\mwscript FILES ${GAMESCRIPT} ${GAMESCRIPT_HEADER})    
 
 set(APPS ${GAME} ${GAMEREND} ${GAMEINPUT} ${GAMESCRIPT})
diff --git a/apps/openmw/engine.cpp b/apps/openmw/engine.cpp
index 507cbc4537..8e7071f50c 100644
--- a/apps/openmw/engine.cpp
+++ b/apps/openmw/engine.cpp
@@ -11,6 +11,7 @@
 #include "mwscript/scriptmanager.hpp"
 #include "mwscript/compilercontextscript.hpp"
 #include "mwscript/interpretercontext.hpp"
+#include "mwscript/extensions.hpp"
 
 #include "world.hpp"
 
@@ -161,7 +162,10 @@ void OMW::Engine::go()
     // Create the world
     mWorld = new World (mOgre, mDataDir, mMaster, mCellName);
 
+    MWScript::registerExtensions (mExtensions);
+
     mScriptContext = new MWScript::CompilerContextScript;
+    mScriptContext->setExtensions (&mExtensions);
 
     mScriptManager = new MWScript::ScriptManager (mWorld->getStore(), mVerboseScripts,
         *mScriptContext);
diff --git a/apps/openmw/engine.hpp b/apps/openmw/engine.hpp
index be560a1723..406cf2358c 100644
--- a/apps/openmw/engine.hpp
+++ b/apps/openmw/engine.hpp
@@ -11,6 +11,7 @@
 #include "components/misc/tsdeque.hpp"
 #include "components/commandserver/server.hpp"
 #include "components/commandserver/command.hpp"
+#include <components/compiler/extensions.hpp>
 
 #include "mwrender/mwscene.hpp"
 
@@ -46,6 +47,7 @@ namespace OMW
             std::auto_ptr<OMW::CommandServer::Server> mspCommandServer;
 
             MWScript::ScriptManager *mScriptManager;
+            Compiler::Extensions mExtensions;
             Compiler::Context *mScriptContext;
 
             // not implemented
diff --git a/apps/openmw/mwscript/cellextensions.cpp b/apps/openmw/mwscript/cellextensions.cpp
new file mode 100644
index 0000000000..ea7f9460c4
--- /dev/null
+++ b/apps/openmw/mwscript/cellextensions.cpp
@@ -0,0 +1,42 @@
+
+#include "cellextensions.hpp"
+
+#include <components/compiler/extensions.hpp>
+
+#include <components/interpreter/interpreter.hpp>
+#include <components/interpreter/runtime.hpp>
+#include <components/interpreter/opcodes.hpp>
+
+#include "interpretercontext.hpp"
+
+namespace MWScript
+{
+    namespace Cell
+    {
+        class OpCellChanged : public Interpreter::Opcode0
+        {
+            public:
+            
+                virtual void execute (Interpreter::Runtime& runtime)
+                {
+                    InterpreterContext& context
+                        = static_cast<InterpreterContext&> (runtime.getContext());
+                        
+                    runtime.push (context.cellChanged() ? 1 : 0);
+                } 
+        };
+    
+        const int opcodeCellChanged = 0x2000000;
+    
+        void registerExtensions (Compiler::Extensions& extensions)
+        {
+            extensions.registerFunction ("cellchanged", 'l', "", opcodeCellChanged);
+        }
+        
+        void installOpcodes (Interpreter::Interpreter& interpreter)
+        {
+            interpreter.installSegment5 (opcodeCellChanged, new OpCellChanged);
+        }
+    }
+}
+
diff --git a/apps/openmw/mwscript/cellextensions.hpp b/apps/openmw/mwscript/cellextensions.hpp
new file mode 100644
index 0000000000..4aef25d1ae
--- /dev/null
+++ b/apps/openmw/mwscript/cellextensions.hpp
@@ -0,0 +1,27 @@
+#ifndef GAME_SCRIPT_CELLEXTENSIONS_H
+#define GAME_SCRIPT_CELLEXTENSIONS_H
+
+namespace Compiler
+{
+    class Extensions;
+}
+
+namespace Interpreter
+{
+    class Interpreter;
+}
+
+namespace MWScript
+{
+    /// \brief cell-related script functionality
+    namespace Cell
+    {
+        void registerExtensions (Compiler::Extensions& extensions);
+        
+        void installOpcodes (Interpreter::Interpreter& interpreter);
+    }
+}
+
+#endif
+
+
diff --git a/apps/openmw/mwscript/docs/vmformat.txt b/apps/openmw/mwscript/docs/vmformat.txt
new file mode 100644
index 0000000000..cad1d3304e
--- /dev/null
+++ b/apps/openmw/mwscript/docs/vmformat.txt
@@ -0,0 +1,26 @@
+OpenMW Extensions:
+
+Segment 0:
+(not implemented yet)
+opcodes 0x20-0x3f unused
+
+Segment 1:
+(not implemented yet)
+opcodes 0x20-0x3f unused
+
+Segment 2:
+(not implemented yet)
+opcodes 0x200-0x3ff unused
+
+Segment 3:
+(not implemented yet)
+opcodes 0x200-0x3ff unused
+
+Segment 4:
+(not implemented yet)
+opcodes 0x200-0x3ff unused
+
+Segment 5:
+op 2000000: push 1 if cell has changed since last frame, 0 if not
+opcodes 0x2000001-0x3ffffff unused
+
diff --git a/apps/openmw/mwscript/extensions.cpp b/apps/openmw/mwscript/extensions.cpp
new file mode 100644
index 0000000000..e0fb81cd3a
--- /dev/null
+++ b/apps/openmw/mwscript/extensions.cpp
@@ -0,0 +1,13 @@
+
+#include "extensions.hpp"
+
+#include "cellextensions.hpp"
+
+namespace MWScript
+{
+    void registerExtensions (Compiler::Extensions& extensions)
+    {
+        Cell::registerExtensions (extensions);
+    }
+}
+
diff --git a/apps/openmw/mwscript/extensions.hpp b/apps/openmw/mwscript/extensions.hpp
new file mode 100644
index 0000000000..a38da03400
--- /dev/null
+++ b/apps/openmw/mwscript/extensions.hpp
@@ -0,0 +1,14 @@
+#ifndef GAME_SCRIPT_EXTENSIONS_H
+#define GAME_SCRIPT_EXTENSIONS_H
+
+namespace Compiler
+{
+    class Extensions;
+}
+
+namespace MWScript
+{
+    void registerExtensions (Compiler::Extensions& extensions);
+}
+
+#endif
diff --git a/apps/openmw/mwscript/interpretercontext.cpp b/apps/openmw/mwscript/interpretercontext.cpp
index 784cc9afaf..bbdd5e1ca8 100644
--- a/apps/openmw/mwscript/interpretercontext.cpp
+++ b/apps/openmw/mwscript/interpretercontext.cpp
@@ -5,6 +5,7 @@
 #include <iostream>
 
 #include "locals.hpp"
+#include "../world.hpp"
 
 namespace MWScript
 {
@@ -68,5 +69,10 @@ namespace MWScript
         if (!buttons.empty())    
             std::cerr << "error: message box buttons not supported" << std::endl;
     }
+    
+    bool InterpreterContext::cellChanged()
+    {
+        return mWorld.hasCellChanged();    
+    }
 }
 
diff --git a/apps/openmw/mwscript/interpretercontext.hpp b/apps/openmw/mwscript/interpretercontext.hpp
index c023b67d02..7b1c281b08 100644
--- a/apps/openmw/mwscript/interpretercontext.hpp
+++ b/apps/openmw/mwscript/interpretercontext.hpp
@@ -36,6 +36,8 @@ namespace MWScript
             
             virtual void messageBox (const std::string& message,
                 const std::vector<std::string>& buttons);
+                
+            virtual bool cellChanged();
     };
 }
 
diff --git a/apps/openmw/mwscript/scriptmanager.cpp b/apps/openmw/mwscript/scriptmanager.cpp
index 607cfc8296..fde9c93fa5 100644
--- a/apps/openmw/mwscript/scriptmanager.cpp
+++ b/apps/openmw/mwscript/scriptmanager.cpp
@@ -10,6 +10,7 @@
 #include <components/esm_store/store.hpp>
 
 #include <components/compiler/scanner.hpp>
+#include <components/compiler/context.hpp>
 
 #include <components/interpreter/installopcodes.hpp>
 #include <components/interpreter/interpreter.hpp>
@@ -39,7 +40,7 @@ namespace MWScript
             {        
                 std::istringstream input (script->scriptText);
             
-                Compiler::Scanner scanner (mErrorHandler, input);
+                Compiler::Scanner scanner (mErrorHandler, input, mCompilerContext.getExtensions());
             
                 scanner.scan (mParser);
                 
@@ -99,7 +100,7 @@ namespace MWScript
             try
             {
                 Interpreter::Interpreter interpreter (interpreterContext);
-                Interpreter::installOpcodes (interpreter);   
+                installOpcodes (interpreter);
                 interpreter.run (&iter->second[0], iter->second.size());     
             }
             catch (...)
@@ -108,5 +109,10 @@ namespace MWScript
                 iter->second.clear(); // don't execute again.
             }
     }
+    
+    void ScriptManager::installOpcodes (Interpreter::Interpreter& interpreter)
+    {
+        Interpreter::installOpcodes (interpreter);   
+    }
 }
 
diff --git a/apps/openmw/mwscript/scriptmanager.hpp b/apps/openmw/mwscript/scriptmanager.hpp
index c029d6506a..17b8cc2426 100644
--- a/apps/openmw/mwscript/scriptmanager.hpp
+++ b/apps/openmw/mwscript/scriptmanager.hpp
@@ -23,6 +23,7 @@ namespace Compiler
 namespace Interpreter
 {
     class Context;
+    class Interpreter;
 }
 
 namespace MWScript
@@ -45,6 +46,8 @@ namespace MWScript
                 Compiler::Context& compilerContext);
             
             void run (const std::string& name, Interpreter::Context& interpreterContext);
+            
+            static void installOpcodes (Interpreter::Interpreter& interpreter);
     };
 };
 
diff --git a/apps/openmw/world.cpp b/apps/openmw/world.cpp
index df6e0f183c..e1c90c71b5 100644
--- a/apps/openmw/world.cpp
+++ b/apps/openmw/world.cpp
@@ -115,4 +115,10 @@ namespace OMW
     {
         return mLocalScripts;
     }
+    
+    bool World::hasCellChanged() const
+    {
+        // Cell change not implemented yet.
+        return false;
+    }
 }
diff --git a/apps/openmw/world.hpp b/apps/openmw/world.hpp
index 7eed09dda8..9efd095b57 100644
--- a/apps/openmw/world.hpp
+++ b/apps/openmw/world.hpp
@@ -68,6 +68,9 @@ namespace OMW
             
             const ScriptList& getLocalScripts() const;
             ///< Names and local variable state of all local scripts in active cells.
+            
+            bool hasCellChanged() const;
+            ///< Has the player moved to a different cell, since the last frame?
     };
 }