Seem unable to edit form field

I’m working in X++ in AX 2012 and trying to add functionality to the LogisticsPostalAddress form part. Part of the functionality needs to populate the form (before the changes are saved), but I don’t seem to be able to populate the fields.

I have found reference to using the following code:


This doesn’t seem to work. If I use:

LogisticsPostalAddress_ZipCode = “NewCode”;

The form doesn’t change, but if I save and reopen the form the data has been changed.

I need to populate the fields on the form so that the user can see the new values before closing the form. Any suggestions?