Pop up message creation

Dear Experts,

My requirement is that

when an employee applies for Earned Leave 7th time the end user should get a pop up message that "Only One chance left to EL"

And also i need to restrict number times leave to be taken to 8 times. When the employee applies EL for 9th time, The leave type should not be accepted by the system. Where do i configure that?

Cheers,

NR