SAP Message AH571 - Not possible to maintain before &1

Diagnosis
You have attempted to maintain the operand values before &v1&. However,this is not permitted because the values for the operand were updatedbefore &v1& via a billing.

System Response
The changes before &v1& are not transferred because the periods updatedvia the billing must not be changed.

Procedure
Check whether the reason you attemped to change the operand values canbe accomplished by another method.