PM Meter Calculation Question

This is to do with how to update the F0911 with meter readings.

There is a PM set up on a vehicle running meter PM schedules. There is a user open field in PM Backlog (CPLM),  that allows the user to input a mileage other than the one the system calculated and assumes is the mileage on the vehicle at the time of PM. How can this new value be stored in the next PM schedule?

e.g.: user keys latest miles into P12120 for vehicle, 100,000 miles. This triggers a PM due on next run of R12807. When vehicle finally arrives for PM, it has 106,328 miles on it. To see 106,328 reflected in the next PM record requires the user to enter 106,328 into P12120