access GameObject only when instantiated

Im using a GetComponent and it is giving me a null reference because the object has not been instantiated.
I tried this

if (GameObject.Find("MyObject")){
      GameObject go = GameObject.Find ("MyObject");
  MyScript myScript = (MyScript)go.GetComponent (typeof(MyScript));

and it works but then Id have to include the functions with the variables from the other script into this and that would result in a super complicated and ugly code.

I could also do something like this

if (GameObject.FindWithTag("MyObject") == null) {}

but how would I make the function stop until the GameObject is found?

Hi again,
I found out this wasnt working because I was using the Update function, which cannot be blocked.
So I created a new function which contains the code I want to execute, only when four different GameObjects are found.
My thought was to do it like this:

if (GameObject.FindWithTag ("Object1") && GameObject.FindWithTag ("Object2") && GameObject.FindWithTag ("Object3") && GameObject.FindWithTag ("Object4"))

and then call the function. This looks strange and is also not working. How would I make this work?