If you are using the 'textbox' component, you can bind the 'paste' event to the input box. Reset the inputed characters after pasting to the input box.
$.extend($.fn.textbox.defaults.inputEvents, {
	paste: function(e){
		var t = $(e.data.target);
		setTimeout(function(){
			var v = t.textbox('getText');
			v = ...	// modify it
			t.textbox('setText', v);
		},0)
	}
})