Would it be because you are tyring to constrain parameters (the char(2)'s) when you aren't supposed to do that? Only pass in the datatype.

But, by "Can't seem to figure it out," what do you mean? You don't know what this procedure is supposed to do, or you don't know why it doesn't work? (Waiting for some sharp-witted almost unemployed DBA who spends too much time here while at work to ask the third possibility of "Or both?")