DAZ and QT( from UI file) widgets - how to combine work?

QT widgets work well with signals. But how to work together with DAZ widgets  and widgets from  UI file? For example, to put the DAZ button into QT Group box or in tab widget (and so on).

var loader = new DzUiLoader();
var dialog = new DzDialog();
var dialogWgt = loader.load("C:/untitled.ui",dialog);
var groupBox=dialog.findChildOfWidget("groupBox"); // QT widget from UI file
var But=new DzPushButton(groupBox) // DAZ widget into QT widget from UI
dialog.exec();
 

This code gives an error "general\dzscript.cpp(658): Unhandled error while executing script."

What I need to do to link different widgets - DAZ and QT?