Batch Derivation for batch to batch transfer

Hi QM Gurus,

I want to do the batch derivation at the time of batch to batch transfer.

But in standard SAP, there is no derivation event to start batch derivation at Batch to batch transfer.( There are events at UD, Release / GR of orders etc.)

Can you please let me know how to create new Custom event for batch derivation.

Also please let me know where and how we can create the logic which can be stored in the field " Exit1 and Exit2" in the condition records of sending or receiving batches.

In short I need to some documentation / guidance on

1. Customer's Own event creation for batch derivation

2. Significance of Fields, "Exit1 and Exit2" in condition records

Thanks in advance.

Sarves