title: Greasemonkey: look for a string between two elements
body: <p>I'm writing a Greasemonkey script, which should do a simple thing: if there's a certain string between the <code>&lt;h2&gt;</code> element (always only one on the page) and the first occurrence of an <code>&lt;h3&gt;</code> element (can be several of them or none at all), then ... (I've already done this part).</p>
  
  <p>I'd be grateful for some help with the conditional.</p>