BOM ?

hi,

I want two clarifications in BOM

1. After the BOM gets exploded in the sales order i should not change the subitems or the quantities also ?

2. My business process is MTO and I have all materials as configurable in my business.

I get the PO from the customer with the specifications of the components which result in a main product. If this is the case. HOW CAN THE SYSTEM IDENTIFY MAIN ITEM BOM AUTOMATICALLY WITH THE SET OF SUBITEMS ENTERED AS COMPONENTS.

Pls send the configurations steps.

regards,

sriram