Unity editor GUI, how to prevent "passthrough"/"clickthrough" etc?

This is about editor GUI, not the new 4.6 GUI.

Been searching all morning, trying to figure out how to stop this.

So if you have two buttons:

GUI.Button ("button 1"); GUI.Button ("button 2");

And let's say they're overlapping. Button 2 will be drawn ontop of button 1 but if you click anywhere in the overlapping part, it will be button 1 that gets pressed.

I've made my own custom drop down menu, the drop down part gets drawn ontop of everything else, this is the last problem I am having; if you click to select an item and there is a gui element under it, the click passes through and also interacts with the element under.

Any help would be appreciated!