Can we restrict employees to apply leave only once in their lifetime

Content

Hi,

Requirement : We have a requirement where we want to restrict the employees to apply a leave only once in their lifetime. Leave will get accrued  every year as it is front loaded. Employee will get the  same new balance i.e. 21 every year and at the end of the year balance will get lapsed. 

But employee should be able to apply that leave only once in their tenure and all the leave balance at once .i,e, ll together 21 leaves... 

Please tell me the possible solution to do it.

Regards,

Dimple