Duplicating address data option for second applicant with a check box

Question

I've been searching and trying things out for hours now, without success.
I'm not sure if this is PDF Forms question or whether I should be posting to the Java forum, but here it is:
I have an PDF application form with several fields for mailing address data (street address, city, state). The application also has an area on another page of the form for a second applicant. The second applicant has an area for their mailing address too.
I'd like to create a check box for the second applicant that says "Same as first applicant", so that if it's checked the address data in all three fields automatically populates the same information that was completed for the first applicant in those fields.
I assume this might be something that required some custom JavaScript but I know very little about how to write code. I've tinkered with a few thinks I found online but nothing seems to work. Any information that could help me out would be much appreciated.

Answer 1

A bit more complicated, but not by much. So basically you can use this script as the MouseUp action of the check-box (notice I used generic field names here, you can replace them with the actual ones in your file):
if (event.target.value=="Off") { // the box is NOT ticked
    this.getField("Target1").value = "";
    this.getField("Target2").value = "";
    this.getField("Target3").value = "";
    this.getField("Target4").value = "";
    this.getField("Target1").readonly = false;
    this.getField("Target2").readonly = false;
    this.getField("Target3").readonly = false;
    this.getField("Target4").readonly = false;
} else { // the box IS ticked
    this.getField("Target1").value = this.getField("Source1").valueAsString;
    this.getField("Target2").value = this.getField("Source2").valueAsString;
    this.getField("Target3").value = this.getField("Source3").valueAsString;
    this.getField("Target4").value = this.getField("Source4").valueAsString;
    this.getField("Target1").readonly = true;
    this.getField("Target2").readonly = true;
    this.getField("Target3").readonly = true;
    this.getField("Target4").readonly = true;