Probier's mal so:
Anbei das Ganze als Projekt (VB2005 Express).
Code:
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Static i As Integer
i += 1
Select Case (i)
Case 1
TextBox1.Text = "dies"
Case 2
TextBox1.Text &= " ist"
Case 3
TextBox1.Text &= " ein"
Case 4
TextBox1.Text &= " test"
Case Else
TextBox1.Text = ""
i = 0
End Select
End Sub
End Class
Anbei das Ganze als Projekt (VB2005 Express).