In Hire an employee in contract page mandatory field for fixed term and optional for Permanent

Summary: Dear all,

Trying to make a change to Hire an employee in contract page we need to make mandatory field for fixed term employee and optional for Permanent employee. When we tried, we are unable to make the contract type mandatory and, in the value, we are unable make any change in the expression because we have some oracle built in rules also applied already.

Can someone please suggest, how we can make this mandatory using Visual builder Studio is this possible?

Thanks in advance for the support.