AutoCad 3D :: Auto Generate Box To Cover Item Of Variable Dimensions

I am working for a company right now and we design cases. The design process involves creating a rectangle of length and width, extruding it to height and than building a case around it. the sides are 20mm offset from the item itself and the top and bottom are 27mm offset from the item itself.

Is there any way I can avoid having to repeat what im doing over and over every time i create a case. We also have standard latches and handles. The top is also standard being 60mm panel height. There is also standard for spacing between the top panels and bottom panels to allow for tongue and groove.