If I understand what you are asking, you could use the
Offset Limb command to do that. Look at this example, I think it is pretty self explanatory.
autocam off
`make a cube, which represents your plane model
make object cube 1,5
offset limb 1,0,2.5,0,0
`make a sphere to mark the "center" of the object
make object sphere 2,1
`position the camera to see the scene
move camera -10
do
`rotate the object with the mouse
rotate object 1,object angle X(1),object angle Y(1)+mousemoveX(),object angle z(1)+mousemoveY()
loop
Notice that I am offseting limb 0 to adjust the point around which the object rotates.