WORKINGDIR "c:\source\folder"
:loop
;; populate %nextfile variable with file name matching wildcard pattern
GETNEXTFILE "Weekly*.dat" 
IFERROR RETURN $ERROR_SUCCESS
;; split the four character ".dat" extension into a new variable
SETRIGHT extension = filename 4 /split 
;; build the new file name
SET filename = "C:\destination\folder\" + filename + "_" + %date + extension
RENAME %nextfile filename 
IFERROR RETURN
GOTO loop