get barcode reader value form barcode gun

I want to create an accounting program with c# language.

I want to use a barcode gun for scanning barcode (pod) from courier covers .

Now, in main form if user uses a barcode reader(barcode gun) to get barcode value,

How can I get barcode value in background of Form (with text box).

what methods or events are used in it.?

Note: My barcode reader is HID (USB interface)

tHANKS IN ADVANCE.