Reload movieclip with different variable

Hey,

here is the the main idea, in an mc i’m loading and displaying some XML. The Xml Url is passed with a variable declared at the first time at the beginning of the mc. Now i want to change the Url/variable with some button click and get the mc with the new Xml Url reloaded and collecting the new data…
how can i get this done?
anybnody gets my idea?