pr13 add-ins

Our payroll is running a bonus check and needs to remove additional amounts that employees have elected for State and Federal
Taxes. Does anyone know what I can do via add-ins to wipe out the tax code on the Additional Amount so that we can remove these and them put them back in after the check run? I tried 00, I tried *Blank - add-ins says that it did the change but nothing really happened. If anyone knows what I can do, or knows how to make a bonus check ignore an extra tax amount, I would appreciate the help.