MM--Collect some Transaction Key Problem

1)What is the difference between BSX and BSA
BSX is transaction Event key for Stock accout or Material accout.For all goods movement BSX will appear.
BSX is inventory posting happens only through goods movement.
BSA is a General Modifier under Transaction Event key GBB.This key it designates Consumtion Only.

BSA will appear in Initial stock POsting using 561 Movement type,This is one time posting happen in a Project that is
Pregolive Activity,We should not use this account after Initial stock.
BSA is physical inventory happens directly without goods movement

2)Sub contracting- A/C postings
While posting GR(101) for subcontracting item against subcontracting PO; posting to a 'change in stock' account (Tr.Event.Key BSV) with a value ( SC item value+SC service charge) will occur.While doing GR in Sub contracting, the following transaction/ event keys will trigger:
•GR/IR clearing account (WRX) will be countered by External services account (FRL)
•Stock account of End product (BSX) will be countered by Change involving stock account (BSV) and,
•Stock account of Components (BSX) will be balanced by the Consumption off-setting entry (GBB-VBO)
Fox an Example:
an example in which we are providing components for Rs.450 and the sub contracting charges is Rs.500
At the tome of goods receipt:
GR/IR clearing account(WRX) 500 -
External service account(FRL) 500 +
Stock account: end product(BSX) 950 +
Change involving stocks(BSV) 950 -
Stock account: comp.(BSX) 450 -
Consumption account(GBB) 450 +

3)Copy movement type and Change Account Key
You copy the 101 movement type but you need a different account detemination. Meaning, when saving the MIGO, you don't want the normal account grouping for 101 (BSX, WRX...etc) but two different account keysThis is not possible in standard SAP because when cpying the movement the account grouping cannot be changedDoes anyone know a user exit or another solution to my problem?
Try this exit LMR1M002 in T-code SMOD for WRX.
For Other you might have to use the valuation class in the material master.