How can I track online orders by sales representative location?

[Fadia]

Hi, we are expending our sales channel. we are hiring multiple representative in different locations. what is the best way to identify online orders coming from specific representative. example i have 2 representative in New York. if i receive an order from a customer in new york how can i identify the sales representative associated to this customer. is there a way to have multiple sub domain directed to my web site and been able to sort the order based on this sub domain? please let me know if there is other options that can help me fix this problem.