title: XML get value based on a changing parameter/variable
body: <p>I am writing a XML file and I need to specify some parameter values according to a condition depends on a parameter will be assigned by my application in run time.</p>
  
  <p>some thing like that</p>
  
  <pre><code>&lt;?xml version = "1.0" encoding="UTF-8" standalone="yes"?&gt;
  &lt;IF x &gt;= 3&gt;
  &lt;THEN&gt; &lt;Length&gt;4&lt;/Length&gt;&lt;/THEN&gt;
  &lt;ELSE&gt; &lt;Length&gt;5&lt;/Length&gt;&lt;/ELSE&gt;
  &lt;/IF&gt;
  </code></pre>
  
  <p>and I need to set the value of x from my qt c++ application every time I query on the length value</p>
  
  <p>Is this possible?</p>