How to change the slider value after mouse scroll for zoom an image in VB

<Grid>
    <ScrollViewer Name="scroller" HorizontalScrollBarVisibility="Auto"  VerticalScrollBarVisibility="Auto"  Margin="2,0,54,111">
        <Image Grid.Column="1" Grid.Row="2" Height="320" HorizontalAlignment="Left" Margin="0,0,0,0" MouseWheel="UIElement_OnMouseWheel" Name="StackPanelImage" Stretch="Fill" VerticalAlignment="Top" Width="502" Source="/MouseWheel;component/Images/d0dbed9f6516b5eb9436e06054d9dcb3.jpg" />
    </ScrollViewer>
    <Slider Height="23" HorizontalAlignment="Left" Margin="12,362,0,0" Name="Slider1" VerticalAlignment="Top" Width="492" />

</Grid>




Private _zoomValue As Double = 1.0

Private Sub UIElement_OnMouseWheel(ByVal sender As Object, ByVal e As MouseWheelEventArgs)
    If e.Delta > 0 Then
        _zoomValue += 0.1
    Else
        _zoomValue -= 0.1
    End If

    Dim scale As New ScaleTransform(_zoomValue, _zoomValue)
    StackPanelImage.LayoutTransform = scale
    e.Handled = True
End Sub