Excel 2000

I have a list of customers which I add to each day and then have to redefine
the range name i.e. extend to include the last row or rows which I entered.

I have been using the built-in feature of Data Form and although I can run
this by clicking a button assigned with the code ActiveSheet.ShowDataForm, I
can't seem to figure out how to extend the range.

Do I need VBA code or a formula that expands?

Thanks, Robert