#pragma code("user32.dll")
LONG SendMessage(
HWND hWnd, // handle of destination window
UINT Msg, // message to post
WPARAM wParam, // first message parameter
LPARAM lParam // second message parameter
);
#pragma code()

HWND Handle=NULL;

Handle=FindWindow(NULL,"Microsoft Excel - abc.xls");
if (Handle) SendMessage(Handle,WM_CLOSE,0,0);