Rate for LP liability and pay out

We have a group of employees moving to new positions with a much higher rate of pay.  These employees will have their PTO balance frozen since these new positions are not eligible to accrue PTO.

We want to use their prior rate of pay to calculate the PTO liability for the ledger and any PTO pay out upon termination of these employees.

I have not found any fields in LP that would enable use to automate this process to any extent.

Any ideas are appreciated.