Q1: Can a file be setup so a macro is always running?

I wrote a macro that allows a user to pick a day of the week with a text box
and based on that selection "groups" of worksheets linked to the selected day
are shown and the other sheets are hidden (that way a user can look at
worksheets only "linked" to a particular day of the week).

Q2: Is there a way to be able to just click on a worksheet tab and have a
set of worksheets that are "linked" to that tab automatically shown (they
would be hidden otherwise)?