Dynamic Metafiles

I'm looking to stream dynamically generated WVX metafiles.

For instance, the metafile would contain a playlist that does this:

1. plays a 30 second clip (commercial)
2. plays a selected movie

The only way i have found to do this is to create individual metafiles for each movie. is there a way to send a variable such as movie location to link it to the file on the mms:// server

Thanks,
Jonathan