Option Explicit
 
Private intMinuten As Integer
 
Private Sub Form_Load()
  intMinuten = 0
  Timer1.Interval = 60000
  Timer1.Enabled = True
End Sub
 
Private Sub Timer1_Timer()
  intMinuten = intMinuten + 1
  If intMinuten >= 20 Then
    intMinuten = 0
    ...
  End If
End Sub