Formulas for Custom Fields

Formulas for Custom Fields

I created a custom field entitled Expiration Date using the below formula (which worked perfectly adding a date that is 30 days after the Create Date):

Datepart(Adddate(${Leads.Created Time},30,'DAY')).

I would like to have Leads expire within 30 days if the no of employees field is <=200 employees and within 90 days if the no of employees field is >=200 employees.

I would appreciate any assistance that you can provide.