Employee should be able to update benefit details only while joining

Summary:

Content (please ensure you mask any confidential information):

Hello,

We want Employee to update the dependent details for benefits only on joining time, thereafter employees are allowed to add only in case of new born in his/ her family or marriage of the employee, this will go for approval of manager since the changes needs to be incorporated in policy.

So basically employee should be able to update or fill details only while joining. How can we try to implement this ?

Version (include the version you are using, if applicable):

24a

Code Snippet (add any code snippets that support your topic, if applicable):