Help with ToggleDropdownMenu

[Valcry]

Good evening,

I have got some problems with ToggleDropdownMenu.

The "usual" call ToggleDropdownMenu(1, nil, Menu,....) is clear.
But actually I'm trying to open a Submenu on Level 2.
Doing this there pops an error-message that the button would be nil.

So, let's guess I got two Firstlevel-Items, each with severel Secondlevel-Items.

MainItem1 Value = "Main1"
Subitem1 value = 1
Subitem2 Value = 2
Subitem3 Value = 3
MainItem2 Value = "Main2"
Subitem4 Value = 4
Subitem5 Value = 5

I tried several calls like

ToggleDropdownMenu (2, 1, Menu)
ToggleDropdownMenu (2, "Main1", Menu) etc.
But still without success.

Any clues/hints for me? What am I doing wrong? At wowace I found a remark that "value" ist the SubmenuID. But which ID?

The reason for my question is, that I would like to make a config-dialog for my addon. And there would be three comboboxes inside and I would like to avoid to create three completely independend menus. I would guess that creating one menu with submenus would save some memory.

Thanks a lot in advance,
Valcry