I have a data validation drop-down list with the values A through F. I
am trying to modify to allow selection of multiple values from the
list.
I created a macro using the code at http://www.contextures.com/excelfiles.html
DV0017
but nothing seems to happen.

I am an experienced programmer, but not with implementing excel
macros. My understanding was I just needed to add this macro and it
would be executed on every select. But I put a breakpoiint on the
first executable lie and it never gets invoked. I followed the steps
in excel for macros with no success. I must be overlooking something,
but am unable to find out what.
Any ideas appreciated.