Assert IsMenu exception when attempting to populate a dynamic menu - winapi

Question

I'm attempting to populate a "submenu" in my dialog box from an array of strings as shown in this answer.
My attempt looks like the following:
#define ID_APP0 14000
#define ID_APP1 14001
#define ID_APP2 14002
#define ID_APP3 14003
#define ID_APP4 14004
#define ID_APP5 14005
#define ID_APP6 14006
#define ID_APP7 14007
void SoftwareDlg::DynamicAppMenu()
{
CMenu MyMainMenu;
VERIFY(MyMainMenu.LoadMenu(IDR_MENU1));
CMenu* SomeMenu = MyMainMenu.GetSubMenu(0);
if (SomeMenu)
{
for (auto i = 0; i < 1; i++)
{
SomeMenu->AppendMenu(MF_STRING, 14000+i, Client::m_vszAppArr[i]);
}
}
}
...but I'm getting an exception from the assert below immediately after(during?) the AppendMenu() function.
_AFXWIN_INLINE BOOL CMenu::AppendMenu(UINT nFlags, UINT_PTR nIDNewItem, LPCTSTR lpszNewItem)
{ ASSERT(::IsMenu(m_hMenu)); return ::AppendMenu(m_hMenu, nFlags, nIDNewItem, lpszNewItem); }
I no longer know how to continue debugging this issue because the LoadMenu() function appears to work correctly, and none of the variables are populated where the exception takes place.
Am I possibly just calling this in the wrong place? It's happening(conditionally) inside of a scheduled member function of the dialog box... does it need to happen somewhere like OnDraw(), OnPaint(), or something?
Edit1: Value of SettingsMenu->m_hMenu
Edit2: IDR_MENU1 resource definition:
IDR_MENU1 MENU
BEGIN
POPUP "Tools"
BEGIN
MENUITEM "New Test F11", ID_TOOLS_NEWTEST
MENUITEM "Export Data", ID_TOOLS_EXPORTDATA
MENUITEM "Upload Data", ID_TOOLS_UPLOADDATA
MENUITEM "Test Control", ID_TOOLS_TESTCONTROL
END
POPUP "Settings"
BEGIN
POPUP "USB_PORT"
BEGIN
MENUITEM "Serial Ports", ID_PORT_SERIALPORTS, INACTIVE
MENUITEM "COM1", ID_PORT_COM1
MENUITEM "COM2", ID_PORT_COM2
MENUITEM "COM3", ID_PORT_COM3
MENUITEM "COM4", ID_PORT_COM4
MENUITEM "COM5", ID_PORT_COM5
MENUITEM "COM6", ID_PORT_COM6
MENUITEM "COM7", ID_PORT_COM7
MENUITEM "COM8", ID_PORT_COM8
END
MENUITEM "Debug Mode", ID_SETTINGS_DEBUGMODE
MENUITEM "Display in OSD", ID_SETTINGS_DISPLAYINOSD
MENUITEM "Test Upload Mode", ID_SETTINGS_TESTUPLOADMODE
MENUITEM "Preferences", ID_SETTINGS_PREFERENCES
POPUP "Target Window"
BEGIN
MENUITEM "Placeholder", ID_TARGETWINDOW_PLACEHOLDER
END
END
END

Answer 1

As hinted to by #Vlad Feinstein's comment, CMenu MyMainMenu; should not have been declared inside the function... That fix allowed me to get past the assertion, but the new menu items were still not appearing. I began catching and logging the return values from the creation and deletion functions which lead me to realize that because I already had an existing menu, I needed to use a pointer to that menu(as opposed to creating my own that I then left un-used).
My final function ended up looking like this:
void SoftwareDlg::DynamicAppMenu(){
CMenu* MainMenu = GetMenu();
CMenu* SettingsMenu = MainMenu->GetSubMenu(1);
CMenu* TargetAppMenu = SettingsMenu->GetSubMenu(5);
if (TargetAppMenu)
{
BOOL appended = false;
BOOL deleted = false;
for (auto i = 0; i < Client::m_vszAppArr.size(); i++)
{
appended = TargetAppMenu->AppendMenu(MF_STRING, 14000+i, Client::m_vszAppArr[i].c_str());
}
deleted = TargetAppMenu->DeleteMenu(ID_TARGETWINDOW_PLACEHOLDER, MF_BYCOMMAND);
OutputDebugString(("String appended: " + std::to_string(appended)).c_str());
OutputDebugString(("Placeholder deleted: " + std::to_string(deleted)).c_str());
}
}