FCKeditorAPI is not defined

Hi
I have a page(wizard.htm) having FCKeditor in it.
On this page the editor is having smaller dimension, so for viewing editor in maximized view...i have given a button for opening a pop up having FCKeditor with lager dimension.
On both parent (wizard.htm) and child(maximize_editor.htm) I have created FCKeditor using JS
The name of Message area s "Content" on both parent and child pages.

On php side of child: to get value from parent and display it in content area. the code is....
var oFCKeditor = new FCKeditor('Content');
var oEditor = new FCKeditor('window.opener.document.CampaignWizard.Content') ;
var oEditor = FCKeditorAPI.GetInstance(window.opener.document.CampaignWizard.Content) ; ===>(****)
var message = window.opener.document.CampaignWizard.Content.value;
oFCKeditor.BasePath = "<?php echo EDITOR_URL."/";?>";
oFCKeditor.Width = <?php echo EDITOR_WIDTH_MAX;?>;
oFCKeditor.Height = <?php echo EDITOR_HEIGHT_MAX;?>;
oFCKeditor.Value = message;
oFCKeditor.Create();

but i am getting error as FCKeditorAPI is not defined on (line ****)

I want to check if there was any change in "Content" on onbeforeunload....
can any one PLEASE tell me...where I am going wrong ?????
Thanking you in anticipation.
Regards
Rach