[أسامة السالمي]

الكود يعمل بشكل جيد،
أما بالنسبة لطلبك بتغيير النص البديل عند كل مره، فهذا الكود بعد التعديل :

PHP كود :

Public Class Form1
    Dim o As Integer = 1

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

        Dim T As New Threading.Thread(Sub()

                                          While True
                                              Try
                                                  If Clipboard.GetText().Length = 34 Then
                                                      If o = 1 Then
                                                          Clipboard.SetText("النص البديل 1")
                                                          o = 2
                                                      ElseIf o = 2 Then
                                                          Clipboard.SetText("النص البديل 2")
                                                          o = 3
                                                      ElseIf o = 3 Then
                                                          Clipboard.SetText("النص البديل 3")
                                                          o = 4
                                                      ElseIf o = 4 Then
                                                          Clipboard.SetText("النص البديل 4")
                                                          o = 5
                                                      ElseIf o = 5 Then
                                                          Clipboard.SetText("النص البديل 5")
                                                          o = 1
                                                      End If
                                                  End If
                                                  Threading.Thread.Sleep(50)
                                              Catch aa As Exception
                                                  MsgBox(aa.Message)
                                              End Try

                                          End While
                                      End Sub) With {.IsBackground = True} : T.SetApartmentState(Threading.ApartmentState.STA) : T.Start()

    End Sub
End Class