[AccessD] Crosstab Query - Additional Parameter

Hi y'all,
I've got a crosstab query that works great.  However, I need to pass an additional parameter (that may or may not be null) and thought I could just add them to the query grid.  This does not work.  I'm assuming that it has something to do with not being part of the columns displayed.  What do I need to do?
 
DoCmd.OpenReport sObjName, acViewPreview, , sWhere, , strSvcRegion & "~" & strLocality 
 
Is the command, sWhere = "" or 2