Обработка нажатия на Button и программное нажатие правой кнопки мыши

#define BTN 239875
#define MAIN 13948534

#include <windows.h>
#include <cstdlib>
#include <ctime>

HWND hwndFound, hwnd, btn;

LRESULT CALLBACK MainProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp);
void Start();

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow){
	WNDCLASSEX wcx;
	int width, height;
	MSG msg;
	RECT srect;

	GetWindowRect(GetDesktopWindow(), &srect);
	width = srect.right;
	height = srect.bottom;

	wcx.cbSize = sizeof(WNDCLASSEX);
	wcx.style = CS_HREDRAW | CS_VREDRAW;
	wcx.lpfnWndProc = MainProc;
	wcx.cbClsExtra = 0;
	wcx.cbWndExtra = 0;
	wcx.hInstance = hInst;
	wcx.hIcon = 0;
	wcx.hCursor = 0;
	wcx.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
	wcx.lpszMenuName = 0;
	wcx.lpszClassName = L"classname";
	wcx.hIconSm = 0;

	if (!RegisterClassEx(&wcx)){
		MessageBox(0, L"!", L"RegisterClass failed", 0);
		return 1;
	}

	hwnd = CreateWindowEx(
		0,
		L"classname",
		L"Off",
		WS_SYSMENU | WS_MINIMIZEBOX,
		width / 2 - 112,
		height / 2 - 40,
		224,
		80,
		0,
		0,
		hInst,
		0
	);

	if (!hwnd){
		MessageBox(0, L"!", L"CreateWindow failed", 0);
		return 1;
	}

	GetClientRect(hwnd, &srect);
	width = srect.right;
	height = srect.bottom;

	btn = CreateWindowEx(
		0,
		L"button",
		L"Go",
		WS_VISIBLE | WS_CHILD | BS_PUSHBUTTON,
		0, 0,
		width, height,
		hwnd,
		(HMENU)BTN,
		hInst,
		0
	);

	ShowWindow(hwnd, nCmdShow);
	UpdateWindow(hwnd);

	while (GetMessage(&msg, 0, 0, 0)){
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}

	return 0;
}

LRESULT CALLBACK MainProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp){
	switch (msg){
	case WM_COMMAND:
		switch (LOWORD(wp)){
		case BTN:
			// ничего не выполняется
			hwndFound = FindWindow(0, L"Name");
			if (!hwndFound){
				MessageBox(0, L"Cannot find window by name", L"!", 0);
				break;
			}
			
			SetWindowText(hwnd, L"On");
			SetWindowText(btn, L"In progress");
			EnableWindow(btn, false);
			Start();
			
			break;
		}
		break;

	case WM_DESTROY:
		PostQuitMessage(0);
		break;

	default:
		return DefWindowProc(hwnd, msg, wp, lp);
	}

	return 0;
}

void Start(){
	int lp;
	
	Sleep(3500);
	srand(time(0));
	lp = (rand() * 23 % 1080) << 16;
	lp = lp + (rand() * 17 % 1920);
	SetCursorPos(lp & 0xFFFF, lp >> 16);
	Sleep(255);
	SendMessage(hwndFound, WM_RBUTTONDOWN, MK_RBUTTON, lp);
	Sleep(200);
	SendMessage(hwndFound, WM_RBUTTONUP, MK_RBUTTON, lp);
	SetWindowText(hwnd, L"Off");
	SetWindowText(btn, L"Go");
	EnableWindow(btn, true);
}