Auto-populate form fields when a check box is ticked

Opening Statement - I'm new to JavaScript in Acrobat. I have researched and read many posts on how to to do this. I'm not having any luck getting it to work.

I have a simple form with 2 checkboxes and numerous text fields. If the user selects checkbox A all the form fields in section B get the input of N/A and the section A text fields are fillable.

If the user selects checkbox B all the form fields in section A get the inpiut of N/A and the section B text fields are fillable.The biggest problem I've had is where to place the javascript - on the checkbox or the text box.

Thanks in advance.