Retro-active Payroll Adjustments

SUGGESTED

Can someone help me with an issue we're having in how to handle a retro-active payroll adjustment for "hourly" employees.  Occasionally, HR is late in provided pay rate adjustments and we need to make an addition to a current check for unpaid "Back-Pay".  For salaried personnel, this fix was simple, we just added another pay category and will include the "back-pay" amount there so it will be included in total wages for the 401k calculations.  However, I cannot find a way of adding back the "back-pay" amount to hourly employees so that it can be part of Gross Wages and be included in the 401k calculations.  Any help or assistance would be greatly appreciated.