global function for user admin status

Coding is not my strong point at all so I need some help please.  I want to create a global function that I can use dtabase wide where required that will for example make a button visible/invisble based on whether the user is Admin or Editor.

So in the Display Only if: option of the button I need a script that checks if the user is Admin or Editor - if not then button is not displayed - How is this scripted?