Expand/collapse a collapsible-set

Expand/collapse a collapsible-set

This is rather a simple question but I can't seem to figure out what to call if I want to expand a div and then not allow one from expanding.  For example I have the following HTML code:

<div data-role="collapsible-set" class="ui-collapsible-set">
    <div data-role="collapsible" data-collapsed="true" class="ui-collapsible-contain" id="dumb1">
        <h3 onclick=" goToFunction()">Go to another Place </h3>
    </div>
    
    <div data-role="collapsible" data-collapsed="true" class="ui-collapsible-contain">
        <h3>Additional Info 1</h3>
        . . . 
    </div>
    
    <div data-role="collapsible" data-collapsed="true" class="ui-collapsible-contain" id="dumb2">
        <h3>Additional Info 2</h3>
       . . .
     </div>
</div>

<script language="JavaScript">
      function  goToFunction(){
            //What goes in here to open dumb2
            ${dumb2}.trigger('expand');
            ${dumb1}.trigger('collapse');
      }
</script>