set an approval workflow and have the salesperson /purchaser code blank on approval user setup

cosl101

Want to be able to setup an approval workflow for customer service. the scenario is as follows:-

1. over 1000 customers with all different salespeople attached to different accounts
2. an approval workflow is setup but the salesperson/purchasing code is left blank due to the customer service persona raising the order could do this on behalf of 30 different salespeople
3. Customer service person raises an order on behalf of a salesperson (whose name is on the sales order header) and then sends for an approval.

the approval workflow errors due to the salesperson code not being filled in correctly.

is it possible without modification to be able raise a SO and send for approval if the approval user setup field is left blank

thanks