javascript insert text on cursor postion

http://www.codewrapper.com/Snippets/View/40/jquery-insert-text-at-the-current-cursor-position-in-textbox

$.fn.insertAtCaret = function (myValue) {
        return this.each(function(){
                //IE support
                if (document.selection) {
                        this.focus();
                        sel = document.selection.createRange();
                        sel.text = myValue;
                        this.focus();
                }
                //MOZILLA/NETSCAPE support
                else if (this.selectionStart || this.selectionStart == '0') {
                        var startPos = this.selectionStart;
                        var endPos = this.selectionEnd;
                        var scrollTop = this.scrollTop;
                        this.value = this.value.substring(0, startPos)
                                      + myValue
                              + this.value.substring(endPos, this.value.length);
                        this.focus();
                        this.selectionStart = startPos + myValue.length;
                        this.selectionEnd = startPos + myValue.length;
                        this.scrollTop = scrollTop;
                } else {
                        this.value += myValue;
                        this.focus();
                }
        });

};