-- Korrektur. vorherige Antwort bitte ignoreren ---

Danke. Der link Link war schon sehr hilfreich. Mit Events kreierter Button der die MsgBox aufruft funktioniert problemlos.
Button der jedoch Text ins VBE Modul einfügen soll, führt nur einmal aus, dann nicht mehr.

[code]
Class Module: "clsCommandBarButton"

> MsgBox
Private WithEvents m_CommandBarButton As CommandBarButton
Public Property Set CommandBarButton(cbb As CommandBarButton)
     Set m_CommandBarButton = cbb
End Property
Public Property Get CommandBarButton() As CommandBarButton
     Set CommandBarButton = m_CommandBarButton
End Property
Private Sub m_CommandBarButton_Click(ByVal Ctrl As Office.CommandBarButton, CancelDefault As Boolean)
     MsgBox "CommandBarButton ''" & m_CommandBarButton.Caption & "'' angeklickt."
End Sub

> Text in VBE Modul einfügen
Private WithEvents m_BT As CommandBarButton
Dim vbComp As Object, code As String, lineIndex As Long, curMod As String
Public Property Set WriteCodeText(vbBT As CommandBarButton)
     Set m_BT = vbBT
End Property
Public Property Get WriteCodeText() As CommandBarButton
     Set WriteCodeText = m_BT
End Property
Private Sub m_BT_Click(ByVal Ctrl As Office.CommandBarButton, CancelDefault As Boolean)
    ShowVisualBasicEditor = True: ActiveWindow.Activate:
    curMod = VBE.ActiveCodePane.CodeModule.Name:    Set vbComp = ThisDocument.VBProject.VBComponents(curMod)
    code = "Selection.Text = ""abc"" "
    lineIndex = vbComp.CodeModule.CountOfLines + 1: vbComp.CodeModule.InsertLines lineIndex, code
End Sub

Module: Buttons
Dim vbTB As CommandBar, vbBT As CommandBarButton, clsBT As clsCommandBarButton, TBname As String, Cname As String
    Public Sub Button_Text()
        On Error Resume Next:     Call ClearVBEtoolbar
        TBname = "Myn 2 Code Templates":                        Set vbTB = VBE.CommandBars(TBname): vbTB.Visible = True
            Cname = "Write Text":          Set vbBT = vbTB.Controls.Add(msoControlButton): vbBT.Caption = Cname: vbBT.Style = msoButtonCaption
                Set clsBT = New clsCommandBarButton: Set clsBT.WriteCodeText = vbBT
    End Sub
    Public Sub Button_MsgBox()
        On Error Resume Next:   Call ClearVBEtoolbar:               TBname = "Myn 3 Code Templates"
        Set vbTB = VBE.CommandBars(TBname): vbTB.Visible = True:    vbTB.Visible = True
        Set vbBT = vbTB.Controls.Add(msoControlButton):             Cname = "Button w MsgBox"
        vbBT.Style = msoButtonCaption:                              vbBT.Caption = Cname
        Set clsBT = New clsCommandBarButton:                        Set clsBT.CommandBarButton = vbBT
    End Sub
[/code]