Hi Bhuma,
From what I'm understanding, your requirement can be translated to: Display "Actual End date" on the Case form when the Case is Resolved.
If it's true, the solution is easy.
1. Just add "Actual End date" field on Case form. Set its visible = false.
2. In Case OnLoad event, use javascript to check current Case status is Resolved or not. If yes --> show "Actual End date" field.
3. Incase you have difficulty while checking case status is Resolved or not, the easiest way is add Case status on the form (hide it), then you can get field value using javascript. Otherwise, you need to call webservice to retrieve Case status.
Hope it help.