To try and help with the question asked, see this post on Kean Walmsley's Blog
http://through-the-interface.typepad.com/through_the_interface/2008/03/embedding-autoc.html
To perhaps suggest an alternative which would simplify things, I had what seems to be a similar need, to ask the user to provide certain dimensions, which sort of needed a visual aid rather than a text prompt to help the user get the right values in the right places. I just did a simple Acad view of the part with dimensions on it, then took a screenshot to use as the BackgroundImage for the form, and I put my Textboxes over the dimension values in the image. see the attached image (only one of several I use). Simple but effective.
BTW, you didn't say what version you are working with, but the code on Kean's site is for 2009 or later.
Edited by: chiefbraincloud on Feb 2, 2010 5:25 PM
No duplicate post this time, but again trouble with the link.
Dave O.