To add information to the UPS Label (eg. PO #, Order Number, etc.), use the following logic:
Globals.CurrentPackage.UserField1 = {your data here};
Globals.CurrentPackage.UserField2 = {your data here};
* These show as Reference Fields 1 & 2... replace out the {your data here} with the actual needed value/variable/expression that you need to show on the label. UserField3 and on do not normally show on the label. *