You may need to set a reference to the Office 11.0 library.
Dim CmdBar As CommandBar
Dim CmdBarPopup As CommandBarPopup
Set CmdBar = Application.CommandBars("Menu Bar")
Set CmdBarPopup = CmdBar.Controls("Tools")
Set CmdBarPopup = CmdBarPopup.Controls("Macro")
CmdBarPopup.Controls("Security...").Execute
Set CmdBarPopup = Nothing
Set CmdBar = Nothing