Setting up levy withholding

We are trying to use the Withholding setup to also process levies. There are two types of levies, a yearly set amount by the IRS based on the vendor's tax classification and a flat amount.

We have been able to get the process to work where we have defined the amounts that should be withheld and sent to the IRS (except for a bug we have logged with the payment currency on the IRS payment), the problem we are having is with the flat amounts.

The plan was to mark the vendor with the levy withholding rule and have the voucher placed on withholding hold. Then when pay cycle is run, the voucher is automatically placed on withholding hold so the Ap clerk can go in and manually split the payment based on the amount of the levy. The problems we are running into are: