populate secondary field from drop down

relatively new at this. Have been searching around and also watched some videos online, but cannot locate.

I have a drop down box with Supplier names called (ie. IBM, HP, etc). How do I take the value that is next to the text in the bindings tab and populate another field on the form

i.e

Object>Binding

Name: supplier

Binding: None

Specify Item Values

Value Text
1 IBM
2 HP
3 Dell

The user will select IBM, HP, etc

I want the corresponding value (ie 1 for IBM, 2 for HP, etc) to populate another field on form called.

prodr_supp_cd

Binding: None

Using LiveCycle Designer ES 8.2

Thank you for any insight.