Dim pToolbarControl As IToolbarControl = CType(m_hookHelper.Hook, IToolbarControl)
Dim pMapControl As IMapControl4 = pToolbarControl.Buddy
'hook から ToolbarControl を取得して MapControl を取得
Dim pToolbarControl As ESRI.ArcGIS.Controls.IToolbarControl2 = CType(m_hookHelper.Hook, IToolbarControl2)
Dim pMapControl As IMapControl4 = CType(pToolbarControl.Buddy, IMapControl4)