Hopefully you have this figured out by now, but when you use a function as a parameter you don't include the parentheses. What is happening is you are telling Javascript to call the function myfunc() and then use the return value as the event handler. So unless myfunc() returns a reference to a valid event handler function, the code will not work.
Use this:
fullIframe.contentWindow.document.attachEvent("onkeydown", myfunc);
RE: Problem in calling events other than onload
Hopefully you have this figured out by now, but when you use a function as a parameter you don't include the parentheses. What is happening is you are telling Javascript to call the function myfunc() and then use the return value as the event handler. So unless myfunc() returns a reference to a valid event handler function, the code will not work.
Use this:
fullIframe.contentWindow.document.attachEvent("onkeydown", myfunc);
Notice the lack of parens after myfunc.