If you need the complete directory, without filename :
=MID(CELL("filename",A1),1,FIND("[",CELL("filename",A1))-2)
If you want to trim the drive letter out :
=MID(CELL("filename",A1),3,FIND("[",CELL("filename",A1))-4)
If you want JUST the last directory name :
Tried, but I don't know how to do that ! Sorry. :-(