Dim cbMonth As Integer ... cbMonth = Forms!AuditAccuracy_Reports!cboMonth
I do not think Integers can be NULL in VBA. So when you set cbMonth to a NULL value you blow it up. I suggest getting rid of all your variables except strCriteria. Instead, just use Forms!AuditAccuracy_Reports!cboMonth instead of trying to assign it to a variable. Then, don't compare it to 0, do an IsNumeric() on it or test it for NULL.