send data through keyboard message

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C++

I create a global keyboard hook in dll.But I find that there is a problem sending data(coordinate in my case) to the dll.I come with the idea of using keyboard message by sending the data in lParam.But I failed.I wonder why?the code is as following.

PostMessage(WM_KEYDOWN,VK_F7,400*(0x10000)+400); // I use F7

in the hook dll

LRESULT CALLBACK KeyboardProc(int code,WPARAM wParam,LPARAM lParam)
{
	if (VK_F9==wParam)
	{
		SendMessage(g_hWnd,WM_CLOSE,0,0);
		StopKeyboardHook();
		return -1;
	}
	else if (VK_F6==wParam&&(0==(lParam>>30)&1))
	{
		if (htargetwnd)
		{
			//PostMessageA(htargetwnd, WM_LBUTTONDOWN, 0,400*(0x10000)+400);
			//PostMessageA(htargetwnd, WM_LBUTTONUP, 0,400*(0x10000)+400);
			PostMessageA(g_hWnd, WM_GETCOORDMESSAGE, 0,0);
			return -1;
		}
	}
	else if (VK_F7==wParam)//&&(0==(lParam>>30)&1)
	{
		if (htargetwnd)
		{
			PostMessageA(htargetwnd, WM_LBUTTONDOWN, 0,400*(0x10000)+400);
			return -1;
		}
	}
	return CallNextHookEx(g_hKeyboard,code,wParam,lParam);
}

It seems that PostMessage(WM_KEYDOWN,VK_F7,400*(0x10000)+400) does not work