Shane,
Just so I understand, you have field 1 already populated when the screen loads? If that's the case, you can use 'Enter Value into Field On Screen', and after field 1 is populated, add that action and set field 2 to be populated with field 1.
Or you can use 'Retrieve Value from Table' and get the value that populates in field one, and set it to populate field 2.
- Adam