Restrict Manual Absence Plan Adjustments Above Ceiling After Enrollment

How can we restrict manual adjustments for an absence based on some condition? For example, Front loaded absence (40hrs) and ceiling limit is 40hrs but based on hire date employee is eligible for 20 prorated hours for the plan term. Since TM is eligible only for 20hrs in the plan term system should not allow manual adjustments. But system is allowing manual adjustments till ceiling limit 40. How can we restrict manual adjustments in this case? Can we trigger error message from accrual matrix formula? 

Thanks,

Venkat M.