Why would you pass a parameter to a stored procedure that doesn't use it?
It sounds to me like you might be better of building dynamic SQL statements and then executing them. What you are trying to do with the SP won't work, and even if you could change what you are doing in such a way to accommodate varying numbers of parameters, you would then essentially be using dynamically generated SQL you are defeating the purpose of having/using a SP in the first place. SP's have a role, but there are not the solution in all cases.