Hi John,
Yes, just add this line to the macro. It will add the datestamp to cell A1 on the active worksheet:
[a1] = "Completed by Joe on " & Format(Date, "mmm-dd-yy")
if you always want it added to a particular worksheet, regardless of whether it is the active sheet then:
Worksheets("MySheet").[a1] = "Completed by Joe on " & Format(Date, "mmm-dd-yy")