Insert Excel File Name into a Cell

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

source of information:  http://mrspreadsheets.com/1/post/2013/01/excel-function-tutorial-7-insert-the-current-file-name-into-a-cell-with-getcell.html