=If day(now())=1 Then
perform task

Or, you can just assign the macro to a button and have it run on click.

"Liz" wrote:

What is the correct function to use in my macro if I have many sheets in my
workbook and I need to update them monthly. after I update them, I have the
updated date in the footer. I know you can select all the sheets by holding
the shift key, but everything I have tried for the date changes everytime I
open the workbook. I want the date to change only when I run my macro.