This is not easy. If I'm right, you want to etch a knurled surface on a cylindrical knob.
As you probably know, you can subtract one solid from another. So, if you can construct a positive version on the knurl, you could subtract it from the cylinder. Essentially, a diamond shaped pattern on a cylinder could be constructed using two helix, one clockwise and one anti-clockwise. You could construct the helix path using fuccaro's LISP routine here http://www.cadtutor.net/forum/viewtopic.php?t=74 and extrude a triangle along the path. These triangular section helix could then be subtracted from the cylinder to produce your knurling.
If you manage to do this, I'd love to see a picture of it.