To make your application process mouse-motion messages, add a WM_MOUSEMOVE case to the window procedure, as follows:
case WM_MOUSEMOVE:
wsprintf(MouseText, "WM_MOUSEMOVE: %x, %d, %d",
wParam, LOWORD(lParam), HIWORD(lParam));
InvalidateRect(hWnd, &rectMouse, TRUE);
break;