Not sure but it looks like there is an api call before the block is inserted i.e. wd_3unit HDS11 perhaps you could add this to the menu.dat fill a long with your block name. If that does not work you can do what we have done and that is create your blocks, insert them into a drawing, link them and then save it as a circuit.
Sorry wrong topic this was ment for the follwing thread:
http://discussion.autodesk.com/thread.jspa?threadID=666366
Message was edited by: JeffatICS