Update [March 2014]
I made some changes. You can't see the formula now, just click on the cell, right click select "Copy" then paste to command line in AutoCAD. I also included some common beam sizes and sections for easy reference. You can copy the dimensions of the beam you want to make, paste it in the section maker then copy the cell. Easy does it.
Draw beam sections easily in AutoCAD (at least version 2000 up) by simply inputting beam dimensions (in MS Excel). Then copy formula and paste to AutoCAD command line. Easy does it.
Download Beam Section Maker for AutoCAD “HERE”: [New Version]
For beam size download this UK Steel Section Properties.