MCI from FileStream

Question

I have a file with multiple media files of different types all concatenated together.
At the start of the file I have a table structure that tells me each media file's start and length.
I have some routines using MCI strings to play the various files individually, but am having trouble finding any info on pointing the MCI routines to just a certain part of a filestream.
If I could use mmio functions to point to parts of a file (NB: NOT memory) then use MCI strings I would be happy.  Or if I could fool MCI into thing part of a filestream was a real file (without having to save a temp file) I would also be happy.
Does anyone have any ideas on how I could do this?