Yes, you can't use / in file names as this is used to separate folder names in the file path.
You can do this, however:
"file:" & Get (DesktopPath) & "FS Rpt ending" & Substitute ( Get (CurrentDate) ; "/" ; "-" ) & ".pdf"
That replaces the / in the date with - and now your file name is legal.
Thank you so much, I was just about to try to figure out a formula create some serial number that related to the date. Your solution is much more elegant. Oh and it works like a charm. I replaced the "-" with a "." and it's B E A utiful.