[Javascript] how do you access a form element from another frame ?

[DEV]

Here is the situation;


_______________________
     
         ( frameGreen )
_______________________
                           |
                           |
                           |
( frameBlue )        | ( frameYellow )
                           |
                           |
                           |
_______________________
     
         ( frameRed )
_______________________


frameYellow has a form named frm1 and a textarea called textArea1

how does a button on the frameBlue update the value in the textArea1

I tried the following, all failed.

onClick="top.frameYellow.document.frm1.textArea1.value='X'"

onClick="top.frameYellow.window.document.frm1.textArea1.value='X'"

onClick="parent.frameYellow.document.frm1.textArea1.value='X'"