MikeMax, have you tried adding your offset value to x and y pointer co-ords? i have just been playing with getspritehit, and although I used the ScreenToWorldX an Y commands, I still had to add the viewoffset to the cursor co-ords.
mousefloat=getspritehit(screentoworldx(getpointerx()+player_x+scrollx),screentoworldy(getpointery()+player_y+scrolly))
I have 2 offsets for each direction, one for the main scroll (player_x) and one for the inbetween scroll between grids (scrollx). This has worked for me doing a large scrolling map earlier today.