How to find pcore directory from within EDK TCL script?

I am working on TCL scripts that go with EDK pcores that I am developing. The MPD file allows me to specify that I want TCL functions in the files I provide to be called at certain times. I would like to be able to determine the directory that the pcore/data/

There are a number of xget_* functions that allow a TCL script to query for information about the project, but I can not find one that will tell me the source of a pcore. Does anyone know how to do this?

Regards,

John McCaskill