Hi Bryon--
It looks like you are trying to set up an insert_tag callback. Do you have code somewhere to initialize the callback? It should look something like this:
doc_add_callback(doc, "insert_tag", "change_tm_type_to_reg_callback");
If you want this to always happen, you can replace "doc" with "0" and put it in your init.acl script. Otherwise, you can put it in an ACL file in editinit, and let doc = current_doc().
--Clay