Hi,
If you will be invoicing using "Items" on the Sales lines, and you require different sales accounts for different items, then as far as I'm aware you need to do the following:
1) Create multiple "Gen. Product Posting Groups" for each different Sales Account you want to post to.
2) Assign the Gen product posting group to the relevant items.
3) Setup the combination of Gen Bus Posting Group and Gen Product Posting Group for each Sales Account.
However if you are invoicing and selecting "G/L account" on the Sales Lines this you can just enter the Sales Account directly onto the Invoice.
Thanks
Gavin