How do I specify which fields/subforms are submitted with a button?

Hi Folks,

I have a form with a whole bunch of subforms with a lot of show/hide dependencies, wrapped into 2 main subforms. I have a submit button in each of the 2 main subforms, but they submit the entire form; how do I change the standard submit button code to gather only 1 of the main subforms (where the button is contained)? The code LiveCycle automatically put in for the buttons is:

<eventname="event__click" activity="click">

  <submitformat="pdf" textEncoding="UTF-16" target="mailto:?subject=Incident Notification" xdpContent="pdf datasets"/>

  </event>

I'm assuming I need to change something in xdpContent? I have basically no coding experience, any help would be reeaaaaaaaaally appreciated!