Moving a mask related to a character mouse event

Hello everyone:

I am having a serious problem programming a mask. I am doing a house in isometric view with several rooms. And I have a character that is moving in these rooms in an isometric movement (i.e diagonal). I have made the code for this character using onClipEvent(mouseDown) and onClipEvent(enterFrame) and within with several conditions IF and variables. Well, this is working, but I have a gigantic stage (2024x1700). So I was thinking in doing a mask about 800x600, and as I was moving the character, the background would move within this mask revealing the room and as the character moves. My problem, is that I don’t know very well how to do it since I’m not an expert in coding. I have seen some tutorials using the keys and others talking about tiles. But, I guess that what I’m looking is something that connects the movement of the character with the movement of the background.
If any of you could help it would be greatly appreciated.

Goo