Add Close button for Portal Users (without emailing)

Add Close button for Portal Users (without emailing)

I'd like to track an additional status (With Customer) to tell me who needs to do work next.  I'd like to change the status to With Customer when I email the customer and back to Open when the customer responds.  I'd also like customers to be able to reopen a closed ticket.  This means anytime the customer hits reply, the ticket(request) moves to Open.

The problem I've found is that when customers try closing a request it will hit my rule and change the status to Open.  Can you add an option to Close without emailing or do you have suggested workarounds?