General Deduction Goal Amount Automatic Update

I want to setup a paycode to reduce general deduction (draw recovery) amount setup on employee general deduction page.

This paycode is only for maintaining balances and should not be added to the paycheck gross. For example. Employee has a loan general deduction setup on create general deduction panel as Goal amount $5000 to be deducted every pay period ($100) .

Employer can forgive some amount based on some criteria and eligibility. A new paycode for forgiveness should be added to the employee's payline, let's say amount $400 but this should not be added to gross (Add to gross unchecked) After payroll is done, employee goal amount on general deduction panel should be updated to $4,600. How can I achieve this ? Any advise would be really appreciated.