Sales Order Entry - Customer Contacts for Reference

In menu Sales->Transaction->Sales Order Entry

I have customer like Company X and 'Contacts' fill with all employee.

and i want to create a sales order entry, when i choose a company in field Customer.
i want to put one employee reference number in field 'Reference'.

I try to create a autocomplete in field Reference based on 'Contact' data from tab Customer.

Tks.
*cakjas