i have a dll i want to inject into another process. it conatains a function which overides an api function

i was wondering what the nijection code should look like? something like
Code:
	HMODULE hinstDLL = LoadLibrary((LPCTSTR)"dll.dll");
    HOOKPROC hkprcSysMsg = (HOOKPROC)GetProcAddress(hinstDLL, "CallWndProc");   
		
	
    // Set the hook
	DWORD ThreadIdCntrl = GetWindowThreadProcessId(windowHandle, 0);  
	::SetWindowsHookEx(WH_CALLWNDPROC, hkprcSysMsg, hinstDLL, ThreadIdCntrl);
?