Hi,
You can attach the Rectangle_MouseEnter and Rectangle_MouseLeave event handlers to the mouse enter and leave events of your HyperlinkButton, and in the event handlers reference the rectangle by name (mouseoverRect) instead:
XAML
<HyperlinkButton Grid.Column="0" Grid.Row="0" x:Name="myLink"
NavigateUri="http://www.silverlight.net" Content="Silverlight"
Foreground="White" MouseEnter="Rectangle_MouseEnter" MouseLeave="Rectangle_MouseLeave"/>
Event Handlers
Private Sub Rectangle_MouseEnter(ByVal sender As System.Object, ByVal e As System.Windows.Input.MouseEventArgs)
Dim myRect As Rectangle = mouseoverRect
myRect.Opacity = 0.5
End Sub
Private Sub Rectangle_MouseLeave(ByVal sender As System.Object, ByVal e As System.Windows.Input.MouseEventArgs)
Dim myRect As Rectangle = mouseoverRect
myRect.Opacity = 0.0
End Sub
Please mark this response as answered if it helps.
Good luck,
Sherwin