What am I doing wrong (vb ,net timer)

Sorry - I am still green when it comes to vb.net...
I have a form (Form1) with a label (Label1) and a button (Button1). When I click the button once - it works fine.  The second, third, fourth etc don't work properly.   I am trying to understand how timers work in .net.   Thanks in advance.  Here is the code

Public ctr As Integer = 0
Public tmr As New Timer()

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

tmr.Interval = 10

tmr.Enabled = True

AddHandler tmr.Tick, AddressOf TimerEventHandler

End Sub

Private Sub TimerEventHandler(ByVal obj As Object, ByVal ergs As EventArgs)

ctr += 1

Label1.Text = ctr

If ctr >= 50 Then

ctr = 0

tmr.Enabled = False

End If

End Sub