Dear Erik,
Thank you for the sample material!
Could you please integrate the external command as a macro into the RVT?
The development team do not have an add-in environment installed, so they prefer macros to reproduce the issue:
http://thebuildingcoder.typepad.com/blog/about-the-author.html#1b
Please note the P.P.P.S.
Thank you!
Cheers,
Jeremy