You would have to use CDO 1.21, Extended MAPI (not from VB) or
Redemption (
www.dimastr.com/redemption).
In those API's you can get the InfoStore that represents the newly
opened PST file and get the PR_ENTRYID property tag (0x0FFF0102).
Hidden in that property is the file path for the PST file.
You can see this if you use OutlookSpy (
www.dimastr.com) on the PST
file and open the PR_ENTRYID property.