If fieldB is blank, leave fieldC blank. if fieldB contains text, fieldC will populate what is in fieldA

Thanks for sharing the details, ​@symone_h 

Just to confirm, because there is a small slip in the wording: I read your rule as, if FULL NAME (Debtor 2) has any text, then MAILING ADDRESS (Debtor 2) should copy MAILING ADDRESS (Debtor 1); and if FULL NAME (Debtor 2) is blank, MAILING ADDRESS (Debtor 2) stays blank. Since Debtor 1's fields are never empty, that is your always-populated source. If that is right, here is the setup.

Here is a suggested script that you can try and modify according to your requirements. Please note that it may or may not work depending on the form type, environment, and application version.

Put the script on the field that should auto-fill (MAILING ADDRESS (Debtor 2)):

1. In Prepare a Form, double-click the MAILING ADDRESS (Debtor 2) field > Properties > Calculate tab > Custom calculation script > Edit.
2. Paste this, using your fields' real names:

var trigger = this.getField("FULL NAME (Debtor 2)").valueAsString;
if (trigger == "") {
event.value = "";
} else {
event.value = this.getField("MAILING ADDRESS (Debtor 1)").valueAsString;
}

The one thing that will make or break it: the names inside getField() must match the fields' actual names exactly, not the printed labels on the form. Spaces and parentheses are fine, but "FULL NAME (Debtor 1)" printed on the page is just static text; the input box next to it might really be named something like "FullName1" or "Debtor2_Name". To check, in Prepare a Form, hover over (or double-click) each field and read the Name at the top of its Properties. Swap in those exact names, and it will work.

I hope this helps, and please refer to the above shared help articles for related JavaScript and form fields properties.

Please reach out if you need any assistance.

Regards,

Anand Sri.