You have a bit of learning to do I'm afraid. In 3D there are three co-ordinates - not two like you have used (that's 2D).
The beginners tutorials may help on my web site (link in sig below).
But, the code you posted is incomplete and MouseMoveX() and MouseMoveY() are functions which RETURN values only. Use them as follows:
MMx = MouseMoveX()
MMy = MouseMoveY()
They return a value depending on how far the mouse is moved in the X and Y directions.
Unlike DBC, DBP returns 0 (zero) when not moved.
You need a Loop at the end of your code (to go with the Do) and inside the loop you need a line to actually move the object and a 'Sync' to update the screen.
To be honest, it's better to use the keyboard to move the object and the mouse to steer, but never-the-less, try altering your code like this...
Set Display Mode 800,600,32
sync on : sync rate 30 : hide mouse : backdrop on : color backdrop 155
Autocam off
make object cube 1, 2: Color Object 1,RGB(255,0,0)
make object sphere 2, 2
make object box 3, 2, 2, 2
posx#=0
posy#=0
posz#=0
ball2a#=90
Position Camera 0,10,-20
Do
MMx=Mousemovex(): MMy=mousemovey()
Inc posx#,MMx
Dec posz#,MMy
Position Object 1,posx#,posy#,posz#
Point Camera posx#,posy#,posz#
Sync
Loop
And don't forget the built in help. All you have to do is click on any keyword in DB and hit the F1 key and it will tell you exactly what the command does, and an example of how to use it.
TDK_Man