Thanks all for your replies.
@ Sammar & Sanjeev,
I dont want to make changes on existing actual dates . Even though the business functionality has no relevance for this requirement, and I as a consultant have made it clear to them so, (but still they want it as it was committed from our pre-sales team) .
The requirement is suppose Activity A has 4 material components assigned to it. The system should consider & maintain the actual start date of the activity of the 1st GRN posting date for any of these 4 matl comp. done. Similarly,actual end date will be when the last GRN posting date is done followed by automatic confirmation.
Selective activities will follow this which we can segregate out using say user fields or so., but the question is that is the above requirement possible?
B.R.