I run multiple stores. I need to know what store each order came from in case a customer inquires via phone. I use DataPort to grab all order data. There is a field in the CSV file called Order_Notes in the 9th field position, also there is another field called Admin_Notes in the 10th field position.

Is it possible for me the set a "FIXED HIDDEN VALUE" in a form in the shopping cart sequence somewhere that will add an IDENTIFYING NUMBER (ie. 101) in that field for each store so we know where that order originated?

Example:

Store A = 101
Store B = 102
Store C = 103
etc...

I don't know how to do what you ask, but you should be able to set different starting values for the store orders.

Store A - Starts at 110000
Store B - Starts at 550000
Store C - Starts at 990000

I don't know if the store number supports alpha numeric values but if it did you could just have.
A1000
B1000
C1000
where the letter always precedes the order number.