Wow, the great Mile-O asking a question... shit that's new.
My guess is access only, vb6 to my knowledge dosent have support for the ! operator nor [] tags for fieldnames, a lot could be missing that may be required.
My suggestion is that you try making a SIMPLE addin in vb6 first and see what happens.
Although, most of the stuff in access supports the . or perhaps the Forms("frmFormNameHere") method, it's worth a shot.