Pass a variable manipulated in Javascript to Java

Within my application, I have a button that opens a modal window and store the response of this, so that.

function lanzarPeticionDependiente(aplicacion, operacion, parametros){
            var sFeatures = 'dialogHeight: 1200px; dialogWidth: 1000px; dialogTop: 150px; dialogLeft: 150px';
            var resultado=lanzarPeticion(aplicacion, operacion, parametros, false, '',sFeatures);}

launch request is simply a function that depending on the past parameters decides whether to open the application in a modal window, new tab or in an iframe.In this case, modal window.

When the result variable is closed, it has an XML stored. That xml would like to manipulate it from a Java class, but when executing the javascript functions with Client.evalJavaScript () I can not do a function with the xml in a return and manipulate it.

I use the ZK framework in case it helps.