Public Sub button3_Click(ByVal sender As Object, ByVal e As System.EventArgs)
For Each tmpCtr As Control In Me.Controls
If TypeOf tmpCtr Is MdiClient Then
(CType(ConversionHelpers.AsWorkaround(tmpCtr, GetType(MdiClient)), MdiClient)).BackgroundImage = New Bitmap ("2004520161632.jpg")
End If
Next
End Sub