Having trouble hooking WM messages

Basically i need some sort of trigger to make my injected dll do what it needs to do, at first i used createremotethread but it soon became apparent to me that its not a viable option as the target program likes to move its memory around alot and constantly renewing the function handle would be very tedious. So i figured id go for something more high level and decided to try and hook windows messages. Heres whats inside the injected dll:

Code:

LRESULT CALLBACK MyWndProc(UINT Msg, WPARAM wParam, LPARAM lParam)
{
	if (Msg == WM_USER+100) 
	{
		UnHook;
	} else if (Msg == WM_USER+101) {
		SendMessage(HWND_BROADCAST, 0, 0x1337, 0x1337);
	}
  return CallNextHookEx(MsgHook, Msg, wParam, lParam);
}
	MsgHook = SetWindowsHookEx(WH_CALLWNDPROC, (HOOKPROC)MyWndProc, (HINSTANCE)hInst, GetCurrentThreadId());

When i inject the thing everything seems ok, the unhook seems to work but when i try to send a message with WM_USER+101 the target program crashes, hard(like 3 crash messages!)

any ideas?

EDIT: ok appears the crashing was a secondary problem caused by something totally unrelated, now that it doesent crash tho it just does nothing at all, i tried changing message to 0 (WM_NULL) to see if it even gets anything but it doesent :/