Using the getValue and setValue from JavaScript ORBEON.xforms.Document.setValue("foo", 42); Value of foo: 42 42 43 43 44 44 45 45 46 46 47 47 Value of bar: Increment foo with JavaScript var fooValue = ORBEON.xforms.Document.getValue("foo"); ORBEON.xforms.Document.setValue("foo", Number(fooValue) + 1);