The Update button takes the text the user types in the Update With field and checks that the string is a valid label or clearance as defined in the label_encodings file.
If the input is not valid, Label Builder generates an error for the user.
If the input is valid, Label Builder updates the text in the Label field and stores the value in the appropriate working label field of the ModLabelData variable that is returned by the tsol_lbuild_create() routine. See ModLabelData Structure.
When the user clicks OK, the user-built value is handled according to the OK button callback implementation.