Can you grab part of a variable? For example, just the left 6 characters?

Is there a way to grab only part of a variable? For example, say I have something defined as:
PROJ_TITLE : $(LASTDIRPIECE(DMS_PARENTPROJECT(_DGNDIR))

That gives me our title for a project which is the project number and name. Something like "654321 Really Big Project"  I want to get JUST the project number out of that returned result. Is there a way to grab just the left 6 characters? Like in Excel you can grab part of a cell's value, is there any way to do that in ProjectWise configurations?

Something like ... ???
PROJ_NUMBER : $(LEFT_6(PROJ_TITLE)

Thanks,
Chris