I have that in some of the example Drafting Templates (The metric ones have it) - it is a smart text code and yes it dynamically updates with the Project Path - so wherever you open the Project From it will update the path name in the Sheet if you hit refresh. If you search Smart Text in Help or reference the Smart Text training from the PUG 2.0 materials I posted this week - you will find a spreadsheet that has all of the smart Text Codes in the sheet.
The smart Text is Project: Path: @<P,PFN>@
Alan