What is use of Control Key in Routing operation ? Need to pass this information to ECC

Hi ,

I need to pass the hours/cost booked  to ECC when operation is confirmed in SAP ME .

What is the use of this control key where the value is passed to SAP ME  from SAP ECC during the production order creation  IDOC but it is not getting passed back to ECC when operation is confirmed .

My question is :

1. How to pass this control key value back to ECC when the operation is confirmed .

2. How to pass the start & end time of the operation from SAP ME to SAP ECC .

Thanks

Kishore K V