DBA For Union Dues based on base pay (Not Gross)

Is there anyone processing payroll in New York where they have the NY Union Dues of 1% which is based on 'base wage', and should not include Shift Pay? If so how did you get the setup to work? We worked with Oracle on this issue and have discovered a BUG when we set up accruals where we are trying to enter a Job Type/Step as the Group Plan DBA to take out the Shift Diff from the Gross Pay. Apparently when a Job Type/Step is entered at the Group Plan Level, it ignores the Basis of Calculation and does