Private Sub Questions_Div_Change (Params As Map)
Dim target As String = Params.Get("target") 'find the checked radio
Dim index As Int = target.SubString(1) 'remove the 'a'
Dim qd As QuestionData = questions.Get(questionIndex)
qd.UserAnswerIndex = index
btnNext.SetProp("disabled", False) 'enable the next button
End Sub