Dim x As Long = 0
 
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) _
      Handles MyBase.Load
        Timer1.Interval = 100
        Timer1.Stop()
    End Sub
 
    Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) _
      Handles Timer1.Tick
        TextBox1.Text += x
    End Sub
 
    Private Sub Button1_MouseDown(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Button1.MouseDown
        x = 1
        Timer1.Start()
    End Sub
 
    Private Sub Button1_MouseUp(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Button1.MouseUp
        Timer1.Stop()
    End Sub
 
    Private Sub Button2_MouseDown(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Button2.MouseDown
        x = -1
        Timer1.Start()
    End Sub
 
    Private Sub Button2_MouseUp(sender As Object, e As _
      System.Windows.Forms.MouseEventArgs) Handles Button2.MouseUp
        Timer1.Stop()
    End Sub