A Gmail filter cannot do what you want. Filters act on a message when it arrives. They do not (can not) affect other messages that have already arrived the previous day.
There may be ways to do that using a separate email client program running on your PC, but not automatically with Gmail itself. You can see the actions that are possible from filters, and comparing message counts is not one of them. You can use a Gmail search to select messages based on date, but I don't think a filter can do that either. Andy -- You received this message because you are subscribed to the Google Groups "Gmail-Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/gmail-users?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
