when the approver opens a RITM the fields should be editable

[Siva55]

Need to implement like when the approver opens the RITM (stage is waiting for approval),some of the fields should be editable on the RITM and save the form.

How to implement this functionality

1.UI Plocy or

2.Client script 

Please help

[Siva55]

@Mohith Devatte ,thanks for your reply but I need to make the variables editable only for the approvers of that particular RITM.So my question here is can I go for client scripts instead of UI Policy