How to change halo texture in render settings by scripting?

Hi, I want to make a script which changes halo texture in render settings, but I don’t know how, I already looked into script reference but I didn’t find anything useful. Is there any way of doing that? I think it should look something like that:

public Texture Text1;

	void Update () {
	if (Input.GetKeyDown (KeyCode.Mouse2)) {/*Set Text1 as halo texture*/;}

No luck I’m afraid, tried all sorts then did a search and found this :

Seems it can’t be done, except for changing color and size.