try

 

 <Script Language="javascript">
            function callInsertImage() 
            { 
                var editor = obj_Editor1;
                editor.FocusDocument(); 
                _Format(editor,"New"); 
                _Format(editor,"InsertFlash"); 
                InputURL();
                document.getElementById("imageFld").focus(); 
                function InputURL()
                {
                    var editdoc = editor._frame.contentWindow.document;
                    var params = editdoc.getElementsByTagName("param");
                    if(params.length>0) 
                    { document.getElementById("imageFld").value = params[0].getAttribute('value');
                    } 
                    else
                    {
               setTimeout(InputURL,500);
                    } 
                } 
            }
        </script>