how to supress report footer based on formula

Question

Hi,
 
In my report i am passing value with ',' (comma) separator to CR input parameter.
My requirement is to supress report footer if single value is entered(ie comma is not found).
 
i am using the Instr string but i am confused how to return the value and meet the criteria.
 
Plese suggest.
 
thanks in advance.
 
thanks
sruthi