Help with Javascript Code

I'm in need of some him writing a quick JavaScript code. I have no experience in JavaScript but understand enough to know what we need. I'm helping to write a very simple writeable document in Adobe Acrobat Pro. We need a code that would specific that when a checkbox is clicked it auto populates information in other text boxes. Simply put: if the mailing address matches the job address then it populates that information. I've included my variables with correct names below.

Thanks for taking the time. Can anyone help?

I need something that will:

if checkbox = "On"

then "Job Address1" = Address1

then "Job City1" = City1

then "Job State1" = State1

then "Job Zip Code" = Zip Code1

then "Job County" = County1

then "Job City, State Zip1" = City, State Zip1

else

if checkbox = "Off"

*each one of the first variables remains empty and writeable.