title: create a variable xsl
body: <p>Good morning, if anyone would know it was helping to create a variable through a xsl and xml</p>
  
  <p>I have this xml:</p>
  
  <pre><code>&lt;!ELEMENT bdticketCardell (invoice, services, products) &gt;
  ........
  &lt;!ELEMENT services (service+)&gt;
  &lt;!ELEMENT service (nameService, quantityService, priceService)&gt;
  &lt;!ELEMENT nameService (#PCDATA) &gt;
  &lt;!ELEMENT quantityService (#PCDATA) &gt;
  &lt;!ELEMENT priceService (#PCDATA) &gt;
  &lt;!ATTLIST service idService ID #REQUIRED&gt;
  </code></pre>
  
  <p>I want to do= ""variable name="grosspriceservice1" select="//quantityService[@idService = "s1"] * //priceService[@idService = "s1"]/>""</p>
  
  <p>Many thanks</p>