[Greasemonkey] Calling a GreaseMonkey function from an "Onclick" event

[thomas Armstrong]

Hi.

With GreaseMonkey, I add a link to the HTML document:
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var myLink = document.createElement("a");
myLink.href = "#";
myLink.setAttribute("onClick", "myFunction();return false");
txt = document.createTextNode('Click Here!');
myLink.appendChild(txt);
myElement.parentNode.insertBefore(myLink, myElement);
---------------------------

myFunction() is declared within GreaseMonkey functions, and
the link is created OK. But when clicking on it, I get this
JavaScript error message:
------------------
Error: myFunction is not defined
------------------

I tested my tool by using JavaScript code on a normal webpage 
and works OK. I don't know if I must call myFunction on a different way.

Any suggestion is appreciated. Regards.