Timer Elapsed Event?

[code]

So I can't seem to get the elapsed event for the timer to work as it won't run the code after the interval is complete. What am I doing wrong? The only other code besides the timer code is code to add a couple columns to a datagrid.

Imports System.Timers

Class MainWindow
    Private WithEvents mainTimer As Timer

    Private Sub Window_Loaded(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded
        'add columns to datagrid
        Dim linkColumn As New DataGridTextColumn : Dim titleColumn As New DataGridTextColumn
        linkColumn.Header = "Links:" : titleColumn.Header = "Titles:"
        linkColumn.Width = DataGrid1.Width / 2 : titleColumn.Width = DataGrid1.Width / 2
        linkColumn.Binding = New Binding("Links") : titleColumn.Binding = New Binding("Titles")
        DataGrid1.Columns.Add(linkColumn) : DataGrid1.Columns.Add(titleColumn)

        mainTimer.Interval = 100 : mainTimer.Enabled = True
    End Sub

    Private Sub mainTimer_Tick(sender As System.Object, e As ElapsedEventArgs) Handles mainTimer.Elapsed
        MsgBox("wow")
    End Sub
End Class