Javascript function issue

i am trying to use fckeditor for a chat.

suppose http://abc.com/index.php
on index.php i have a function defined which works for ajax. ( call_ajax() )

now all i want it when i press enter in the fckeditor box it calls a function defined in index.php
so i have copied this code in fckconfig.js

function DENOnKeyDownFunction(){
[color=#FF0000]call_ajax();[/color]
}

function DenIE_OnKeyDown(){
     var e = FCK.EditorWindow.event ;
     var alreadyRun = false;
     // alert(e.keyCode);
     switch ( e.keyCode ){
        case 13 :    // ENTER
           if ( !(e.ctrlKey || e.altKey || e.shiftKey) ){
                 e.cancelBubble = true ;
                e.returnValue = false;
                if (alreadyRun == false) {
                    DENOnKeyDownFunction();
                     alreadyRun = true
                }
                return false;
            }else{
                 return true;
            }
                 break ;
      }
}

var DenGecko_OnKeyDown = function(e) {
     var alreadyRun = false;
     // checks if enter key alone was pressed, and if so, say hello!
      if (e.which == 13 && !e.shiftKey && !e.ctrlKey && !e.altKey) {
         e.preventDefault();
         e.stopPropagation();
         if (alreadyRun == false) {
         DENOnKeyDownFunction();
         alreadyRun = true
         }
         return false;
     }
return true
};


function FCKKeyPress_SetListeners() {
   if (document.all) {        // If Internet Explorer.
         FCK.EditorDocument.attachEvent("onkeydown", DenIE_OnKeyDown ) ;
    }else{                // If Gecko.
      FCK.EditorDocument.addEventListener( 'keypress', DenGecko_OnKeyDown, true ) ;
   }
}
FCK.Events.AttachEvent( 'OnAfterSetHTML', FCKKeyPress_SetListeners ) ;