I have a button:
When I click this button the first time, I want it to exe
What might be easier, is to have two buttons and show/hide them in your functions. (ie. display:none|block;) Each button could then have it's own onclick with whatever code you need.
So, at first button1 would be display:block and button2 would be display:none. Then when you click button1 it would switch button2 to be display:block and button1 to be display:none.