This is very simple using the Change event together with the GetDate method, an example in Win32::GUI::XMLBuilder is :-

<GUI>
    <Window name='W'
        dim='0, 20, 200, 80'
        title='DateTime demo'
    >
        <DateTime 
            height='$self->{W}->ScaleHeight/2'
            onChange='sub { 
                $self->{L}->Text(join(":", $_[0]->GetDate())) 
            }'
        />
        <Label name='L'
            text='change date'
            height='$self->{W}->ScaleHeight/2'
            top='$self->{W}->ScaleHeight/2'
        />
    </Window>
</GUI>
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These questions are best directed to the Win32::GUI mailing list.