Lapsing of leaves

Hi,

I have a scenario in time management. I have Privilege leave = 24 per year. This is accrued 2 per month. The leave is carried forward until a maximum accrual of 90 days. This much had been configured. But in case employee does not take a minimum of 7 leaves, it gets lapsed. So 7 lapses and maximum carried forward per year would be 17 (24-7). How can I configure the same?

Regards,

Rahul