Read-Only mode please help

Hello,

I searched the forum and found this method

var oEditor = FCKeditorAPI.GetInstance('FCKeditor1');
oEditor.EditorDocument.body.disabled=true

but this didnt worked for me, because im using the textarea replace function, and im already using window.onload if I put this function there it tells me body is null. Any ideas?

Thanks

Jorg3