On the other hand, as you are changing these packages yourself, why don't you change the revision to a higher one, and pass the "<" flag with the -l option to pkgin?
This is in case you have to keep your local packages when new revisions get in, I mean, if your packages' versions are the same as the ones in the repository, doing just pkgin -l '<' upgrade should do what you want right now. Regards. adr