Accounting Key GL means--at the time of Commission settlement from B to A.
Your First post says'''Company A act as an agent for company B """""
Later posts says that''''''
Note: finally i was little confused here that--If A will collect the order for B-company--so make A as a Soldto/Ship to/Payer for the billing came from company B.
Also you can have one more accounting key or sub total which gives the actual sales value(Price minus Discounts plus taxes/freight) to one GL--there by you can analyse the respected accumulated amounts from the GL assigned....
If you want to take the total sales for A customer(As one partner)--it can be very well retrieved in later times...
Hope this helps...
Phanikumar