...
Private Sub Insps_NewInspector(ByVal Inspector As Outlook.Inspector)
Dim ToolBar As CommandBar
Set ToolBar = Inspector.CommandBars.Add(Name:="Test", Position:=MsoBarPosition.msoBarTop, Temporary:=True)
ToolBar.Visible = True
'' Создание кнопок на ToolBar
Set Ctrl = ToolBar.Controls.Add(Type:=MsoControlType.msoControlButton, Temporary:=True)
With Ctrl
.Caption = "Test"
.Tag = "Test"
.Visible = True
.OnAction = "!" + AddIn.ProgId
End With
End Sub

Private Sub Ctrl_Click(ByVal Ctrl As Office.CommandBarButton, CancelDefault As Boolean)
MsgBox ("Test")
End Sub