I apologize for answering wrong question, but I don't want to leave you at the risk of trouble. So…
Do yourself a favor,
don't risk you most valuable code investment!
Do not use VSS!
This product is obsolete, proprietary (you really need Open Source), intrusive and conceptually broken.
For example, it is not transactional (!).
What to do? Please consider this discussion:
Revision control systems, which to choose from?[
^].
(Please, do not tell me "this is a requirement!" — this is not my concern. I only care about best advice.)
—SA