change image source

Hi

i am trying to change the source property of a image when the mouse enters the image on a wpf form

in the mouseenter event i have the following code

    Private Sub Image2_MouseEnter(ByVal sender As System.Object, ByVal e As System.Windows.Input.MouseEventArgs) Handles Image2.MouseEnter
        Image2.Source = "exit2.jpg"
    End Sub

I cant workout how to change image2source to a new picture 

Exit2.jpg is in my image resources

Exit1,jpg is the source i am trying to change

Any ideas

Mark