BN_CLICKED
idButton = LOWORD(wParam);
hwndButton = (HWND)lParam;
The BN_CLICKED notification message is sent to the parent window when the user clicks a button. Unlike the other button-notification messages, this message is intended for applications written for any version of Windows.
idButton
Value of low word of wParam. Specifies the button-control ID.
hwndButton
Value of lParam. Specifies the button-control window handle.
Disabled buttons will not send a BN_CLICKED notification message to a parent window.
WM_COMMAND