need help with movement background (real time)

hi , i do an isometric flash rpg game with as2 i need a little help:

i would if i let walk my character (or if i move my mouse out of the stage) until the stage flash will show other part of back ground image i dont know how to explain it but i mean if you move your character in a rpg game "background will change with you and you go away from the starting point than if you walk back to starting point, background will change with you real time sorry for english i hope you understood me

(in this game if you move your cursor in game scene background changes real time and shows other parts of image http://www.youtube.com/watch?v=XVUPgUgl0hU)