OnUserEvent parameters

Hi everyone! I know we can pass event parameters with <UserEventArg /> to JavaScript Handler function but how to use these parameters in UX?

I raise the event with the following:

<RaiseUserEvent Name="modalEvent">
    <UserEventArg Name="message" StringValue="Dialog Message?" />

And have the following <Panel>:

<Panel ux:InnerClass="ModalScreen" ux:Name="self" Visibility="Collapsed">
    <OnUserEvent Name="modalEvent">
        <Set self.Visibility="Visible" />

    <Panel Background="Black" Opacity="0.5" />
    <StackPanel Alignment="VerticalCenter" Padding="30" Margin="50" Background="White">
        <Text TextAlignment="Center" Value="{HOW TO GET 'message' ARGUMENT?}" />
        <Button Text="OK">
                <Set self.Visibility="Collapsed" />

            <BringToFront />

How to show message in the <Text> node of the <Panel> when I raise the event?

Any examples for this, please?