How to update absense days after calendar event

Dear, 

In Absence management system, we are facing issue in holidays. Suppose employee take leave from 23-dec-2013 to 26-dec-2013 then system count 4 days absence. After this we mark holiday on 25 December, but system not effect employee holiday which has been marked 4 days.

However, if we first mark calendar and enter leave then system work fine and exclude holidays from absence.

Is there any procedure which updates those leave which has been entered before calendar event?

 Thanks