Something like this?
sync on
Sync Rate 60
autocam off
Make Object Cube 1, 1
Position Camera 0, 50, 0
Point Camera 0, 0, 0
sync
Do
Set Cursor 0, 0
If Upkey()
If (Object Screen Y(1) > 0) Then Move Object 1,1
Endif
If Downkey()
If (Object Screen Y(1) < Screen Height() - 10) Then Move Object 1,-1
Endif
If leftkey()
If (Object Screen X(1) > 0) Then Move Object Left 1,1
Endif
If rightkey()
If (Object Screen X(1) < Screen Width() - 10) Then Move Object Right 1,1
endif
Print Object Screen X(1)
Print Object Screen Y(1)
sync
Loop
One more thing about "Object Screen X/Y": If the camera is looking exactly the oposite direction (instead of facing the object) the values will be in bounds too.
(I think the coordinates are mirrored then)
