Question : choose workbook to run macro against/on

I need to be able to run a macro that exists in one workbook on data that is in another workbook.  I'd like to automate this a little.

I woudl like to be able to have a button to trigger the macro, and then be presented with a list of open workbooks to choose which to run the macro "on".

I woudl have hard coded it, btu both workbooks a can have variable filenames, and it is possibl more than one of the target data workbooks coudl be open at once.

I know how to make the button, what I do not know how to do is be able to select the target workbook.  Is this possible?  

Thanks!
Scott

Answer : choose workbook to run macro against/on

Change this line:
 $event_display_date = date("D, F j, o", $event_time);

To this:
 $event_display_date = date("D, F j, Y", $event_time);