append host

In FCKeditor I used to be able to make this change:

Location: /editor/filemanager/browser/default/frmresourceslist.html

// Build the link to view the folder.
var sLink = '<a href="#" onclick="OpenFile(\'http://somedomainhere' + ProtectPath( fileUrl ) + '\');return false;">' 

Where can I do the same for ckeditor?

Thanks,
Matthew