"Outlook, eh?" wrote...
Thanks , but I got the message:

The formula you typed contains an error..

Awkward word wrapping. I'll fix it below.

Did I have to change M to the empty cells in L, in the second part?
....

No. If the names are in column M, then that's the only column to which the
formula would need to refer.

=TEXT(SUMPRODUCT((TRIM(M2)<"")*(TRIM(M$2:M2)<"") ),
"""ImportID-""00;;")