Xml caching solution with var

Hi,

after doing a bit of a search, I came upon this solution for the xml caching issue:

 xml.load(”xmlFile.xml?”+Math.random());

the problem is my xml file is a variable being passed from the html, so I was wondering how to write this without the inverted commas?

xmlData.load("_root.varXML?"+Math.random());listen = new Object();

any help would be great.