How to add payroll balance value in fast formula to be used in Compensation?

Hi,

We currently have a requirement for a Bonus plan in compensation that the eligible salary for calculating Bonus payout should be the pay values in the calendar year including elements of basic salary, basic salary retroactive, basic salary adjustment etc. We've created a balance group called Bonusable Pay that and did some testing that it works to pull in all the elements required in the calendar year (as shown in screenshot1 below). Now the question is, how to build a FF to bring the total balance value into Compensation worksheet? Please could you advise how to include the balance value