InfoPath Dev

I am using Sharepoint 2010/InfoPath 2010.  I have a SP list where I have customized the form with InfoPath.  I have a multi-selection list box with 15 manually entered choices.  I need to create a rule that will run an action when the values chosen are anything other than 2 of the choices.  Is this possible?

 the good thing is with a customized form you can add additional fields, hidden. Your action should set the value of the hidden field using the double eval. here is a post that's is using sharepoint and the double eval: http://www.infopathdev.com/forums/p/17505/61001.aspx#61001

now your hidden textbox contains a string. you can use another rule to check if it contains, or not contains.