>I'm trying to create a loading picture. However, when i display the screen
>in AMIGA-mode, the screens can be swapped by using [A]+M, and the
>mouse-pointer is still visible. Does anyone have any ideas how to prevent
>that. I also though about using the QAMIGA-mode, but then I have to wait

Forget that BMode-Stuff.  It is possible with an OS-Routine called
"ClearPointer_(*window)"

Just create a borderless window in the screensize. 

Then call

ClearPointer_(Peek.l(Addr Window(nr))

where nr is the number of your window.