copry control routine at header level
How to maintain a copy control routine at header level ie. transaction to transaction.
This is required to copy field values from parent opportunity to the follow up transaction.
you can implement crm_copy_badi in se19.
for filter you will point copying routine that you created in spro in "badi: enhancements for copying control". this routine should also be pointed in spro in "Define copying control for transaction types" in Copying routine column.
in this badi you will have to find apropriate method that is being used by the system while making follow-up between your transactions.