Sharepoint Workflow Claim & Release Task Scenario

Hi,

I hav created a sharepoint workflow that has task assigned to a sharepoint group, now i want the task to be editable by only

1 person in a group, so i m assigning right dynamically to edit the task on createTask, hence the only the group user will

allowed to edit on that taskitem,
There is something in sharepoint tasks called "Claiming & Releasing Task" which i thought should resolve my problem,
but after claiming the other users of the same group shouldnt able to edit the task, which is happening in my scenario !

i m getting into taskchanged event when someone from group claims the task, so there i could use the remove group permission

and assign it only to the claimer of the task, but same way for realese task the same method is called again here i hav to

assigned right back to group, but i m not able to catch on which activity calls the taskchanged method claimTask or

releaseTask

Can anybody Help me On this ....