App to text back purchase order numbers

[cshue]

I'm looking for an app that would act as a dispatcher for issuing purchase order numbers to employees. The idea is when an employee calls up our vendors to order materials they would first text a supervisors phone (or service) and receive a PO number to give to the vendor for the invoice. Each supervisor would then have record of who each PO number was issued to along with date/time. Was also thinking of something simple like a deli counter "take a number" wheel. I've found a service that operates to give out unique codes for use with coupons if you were offering a limited time deal. It doesn't have to be a PO number app just something that when a text is sent with a specific subject line or to a specific number if it's a service some where, the sender receives back a unique number each time, sequential would be best not random. So user 1 texts and receives 100, user 2 texts and receives 101, user 1 then texts again and receives 102, and so on.

Does anyone know of an app that will fit?

Thanks

Craig