update Excel File Name (Rename an Excel Sheet), and it auto updates a specific cell in the workbook

Budman36  It sounds like you want the filename in a cell.  The function CELL() offers that sort of.  CELL("filename") actually gives the full path/reference but with some additional work you can have it trim just the filename out:

=LET(path,CELL("filename"),start,SEARCH("[",path)+1,end,SEARCH("]",path),fn,MID(path,start,end-start),fn)

if you don't have the newest version of Excel with the LET() function you can use:

=MID(CELL("filename"),SEARCH("[",CELL("filename"))+1,SEARCH("]",CELL("filename"))-SEARCH("[",CELL("filename"))-1)

but maybe the full path would be even better for you?