Public Class Form1
 
  Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Me.Timer1.Start()
  End Sub
 
  Private Sub Buttons_Click(sender As Object, e As EventArgs) Handles _
    Button3.Click, Button2.Click, Button1.Click
    DirectCast(sender, Button).Tag = Process.Start("calc.exe") 'Rechner starten
  End Sub
 
  Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
    For Each b In {Me.Button1, Me.Button2, Me.Button3}
      Dim p = DirectCast(b.Tag, Process)
      If p IsNot Nothing AndAlso Not p.HasExited Then
        b.BackColor = Color.Green
      Else
        b.BackColor = Color.Red
      End If
    Next
  End Sub
 
End Class