Big map

Hi
I'm trying to make a tile map bigger than the screen which the player can scroll around in, a lot like civilization, warcraft 1/2 etc.

So far I have a test map set up, and an action map which calls a function to change variables $cameraSpeedX and $cameraSpeedY.

I was hoping to use onUpdateScene to shift the camera around depending on the global variables mentioned above. To me it looks like onUpdateScene isnt getting called at all though. Can anyone tell me whats going on or suggest a better method to move the camera over a big map?

thanks

function createKeyMap()
{
//create a new actionmap
new actionMap(playerMap);

PlayerMap.bindCmd(keyboard, "w", "playerUp();", "playerUpStop();");
//PlayerMap.bindCmd(keyboard, "s", "playerDown();", "playerDownStop();");
//PlayerMap.bindCmd(keyboard, "a", "playerLeft();", "playerLeftStop();");
//PlayerMap.bindCmd(keyboard, "d", "playerRight();", "playerRightStop();");
//PlayerMap.bindCmd(keyboard, "space", "playerFire();", "");

playerMap.push();
}

-------------

function playerUp()
{
$CameraSpeedY = 10;
}

function playerUpStop()
{
$CameraSpeedY = 0;
}

-------------

function updateCamera()
{
echo("\nupdateing camera");
//get the current camera co-ords
%cameraPosition=sceneWindow2D.getCurrentCameraPosition();
%cameraPositionX=getWord(%cameraPosition,0);
%cameraPositionY=getWord(%cameraPosition,1);
%cameraPositionY = %cameraPositionY + $cameraSpeedY;
%cameraPositionY = %cameraPositionY + $cameraSpeedX;
sceneWindow2D.setCurrentCameraPosition(%cameraPositionX SPC %cameraPositionY @ " 100 75");
}

--------------------

function t2dSceneGraph::onUpdateScene(%this)
{
updateCamera();
}