make a 3D cube with drag & drop

Hi All!,
Please, someone has code for make a 3D
cube but using 2D drag & drop with mouse?
My brain is going to explode!
I need to create zones in 3D (rectangles with volume)
with a fixed high but using the mouse to define
the x and z coords and the width and depth..
Please help!!!!!!

BlitzSupport has done something with that in the code archives... http://www.blitzbasic.com/codearcs/codearcs.php?code=379

Thank you very much!
I appreciate a lot your help, but I need
to go depth with this.. I would need to know
how to "create" or modify a rectangle with
that system, alter only the global size to fix
in the box defined with the mouse or to alter
the vertex of a cube to obtain the same result..

If you don't understand this you need to take several paces backwards and learn it. We're not going to wipe your arse for you.

Ok, thanks, but possibly there exist
a notorius confusion. I'm only asking if
someone has code -done- related to my small
issue in order to save some time, but I'm
not asking for someone to work for me, obviosuly.
Excuse me for making you spend your time, genius.