Need help with a workflow

We have a group of customers who are part of a purchasing co-op. When these customers place orders they need a description item added to the order to display the co-op bid number. I created the description item. I also put a custom checkbox on the customer screen to indicate members of the co-op.

I then designed a workflow so that when a sales order is entered for a co-op customer it would add the desc item after all the regular items.

It works on orders put in directly to netsuite from our internal sales folks. It does not work for web orders placed by the customer.