#include <windows.h>

#define M_HINSTANCE	(HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE)


LRESULT CALLBACK EditProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	static WNDPROC oldProc = NULL;

	if (! oldProc)
		oldProc = (WNDPROC)GetWindowLong(hWnd, GWL_USERDATA);

	switch(msg) {
		case WM_KEYDOWN:
			if (wParam == VK_RETURN) {
				MessageBox(NULL, "Enter has been pressed", "Yeaho", MB_OK);
				return 0;
			}
			break;
	}

	return CallWindowProc(oldProc, hWnd, msg, wParam, lParam);
}


LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	static HWND hWndEdit;
	static HINSTANCE hInstance;
	WNDPROC oldProc;

	switch(msg) {
		case WM_CREATE :
			hWndEdit = CreateWindowEx(WS_EX_CLIENTEDGE | WS_EX_STATICEDGE, TEXT("Edit"), NULL,
					WS_CHILD | WS_VISIBLE | ES_AUTOHSCROLL,
					2, 422, 605, 25,
					hWnd, NULL, M_HINSTANCE, NULL);

			oldProc = (WNDPROC)GetWindowLong(hWndEdit, GWL_WNDPROC);
			SetWindowLong(hWndEdit, GWL_WNDPROC, (LONG)EditProc);
			SetWindowLong(hWndEdit, GWL_USERDATA, (LONG)oldProc);
			return 0;

		case WM_SETFOCUS:
			SetFocus(hWndEdit);
			return 0;

		case WM_DESTROY:
			PostQuitMessage(0);
			return 0;
	}

	return DefWindowProc(hWnd, msg, wParam, lParam);
}


int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   PSTR szCmdLine, int iCmdShow)
{
	HWND         hWnd;
	MSG          msg;
	WNDCLASS     wndclass;
     
	wndclass.style         = CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS;
	wndclass.lpfnWndProc   = WndProc;
	wndclass.cbClsExtra    = 0;
	wndclass.cbWndExtra    = 0;
	wndclass.hInstance     = hInstance;
	wndclass.hIcon         = LoadIcon(hInstance, IDI_APPLICATION);
	wndclass.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject(LTGRAY_BRUSH);
	wndclass.lpszMenuName  = (HMENU)NULL;
	wndclass.lpszClassName = "WindowClass";
          
	if (! RegisterClass(&wndclass)) {
		MessageBox(NULL, TEXT("Program requires Windows NT!"),
				"Error",MB_ICONERROR);
		return 0;
	}
     
	hWnd = CreateWindow("WindowClass", TEXT("-- PeChat --"),
			WS_DLGFRAME | WS_SYSMENU | WS_MINIMIZEBOX,
			CW_USEDEFAULT, CW_USEDEFAULT, 800, 498,
			NULL, NULL, hInstance, NULL);

	ShowWindow(hWnd, iCmdShow);
	UpdateWindow(hWnd);
     
	while (GetMessage(&msg, NULL, 0, 0)) {
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}

	return msg.wParam;
}

.