3D surface plot

I have what is probably a noob question, but....

I am trying to create a 3d plot to illustrate the range of values for the following simple function:

A = B*(C/D)

B, C, and D are independent variables whose range are equal (e.g. 1 to 3 inclusive)

I figure it's not possible to map the surface of A on the 3d space defined by B, C and D but I would like to create a surface defined by the lower and upper limits of the variables - that is to say a rectangle with corners at (1,1,1), (2,3,2), (3,3,3) and (3,2,2) with a color map displayed on it corresponding to the values of A and a color key to the side of that.

I have been able to wrap my head part way around persp and wireframe and can create a surface for A~B*(C/D) in either, but have not managed to create either the