restriction of carry over used in year

Summary:

How can we restrict carry over leave not to be availabled after certain period of time for partricular employees

Content (please ensure you mask any confidential information):

Hi,

As we have carry over formula which transfer annual balance to the next year which has been working fine. However, we have to restrict this usage for particular months only.

For exampl,employee leave have 10 days annual leave and carry over is 5. Now if employee used this balance till march but after that he can not utilized this carry over balance but this is only applicable for few employee only.

Where we can modify this condition in fast formula.