Winapi . TrackPopupMenuEx equivalent in CreateWindow - c++

Question

When we create a pop up menu we call a function TrackPopupMenuEx . It displays a shortcut menu at the specified location and tracks the selection of items on the shortcut menu .
If you specify TPM_RETURNCMD in the fuFlags parameter, the return value is the menu-item identifier of the item that the user selected. If the user cancels the menu without making a selection, or if an error occurs, the return value is zero.
This command is blocking ie unless we click on menu or outside we are blocked.
I have created a window which has various static items which acts like a popup menu. Is there some function equalient to (TrackPopupMenuEx with TPM_RETURNCMD ) which can tell me which was the last WM_COMMAND CLICKED which is blocking . If a function does not exist , how can we create a good blocking in the view that it doesn't eat up the CPU in wait cycle.
What I did :
In the WM_COMAND I initialize the global variable which is whatIsLastClicked. In my function i wait till this variable is set but it seems to eat cpu.
Some code
WNDCLASSW wc = { 0 };
wc.hbrBackground = (HBRUSH)COLOR_WINDOW;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hInstance = hInst;
wc.lpszClassName = L"mywindowsclass";
wc.lpfnWndProc = windowprocedure;
//<== all handlers WM_COMMAND defined in this fucntion
if (!RegisterClassW(&wc))
{
return -1; // registration failed
}
HWND hWnd = CreateWindowW(L"mywindowsclass",
L"My window", WS_OVERLAPPEDWINDOW | WS_VISIBLE,
100, 100, 500, 500, NULL, NULL, NULL, NULL);
//POINT : need some blocking code here which is efficient to find what i clicked