Help with OnPress

[Vexen]

I have a button that you click to cure/cast etc etc.

I am trying to get it to say something in chat (ie guild chat or say or whatever) and cant get the "onpress" function (I think it is) to work properly.

Question #1:
What is the proper formatting for this function?

Question #2:
Is there a way to have a variable that is easily edited for the users of the UI to change what is said in the chat?

Any help would be appreciated. Thanks.