Change default approver name in ESS leave request

Hi,

Please help me..

I am creating leave request Workflow.

When i go to ESS and try to create Leave Request, ESS already defaults the Approver, and its in display mode only.

I see the F4 help in Approver field and when i try to select from F4 help, it does not take new value. It's still the same value as it was default to initially.

How can i use F4 help and change the default approver name?

Can anyone please help me...I dont know where the things are missing.

Thanks in Advance

Shipra