http://llmotorsport.se/resources/scripts/jquery.insertatcaret.js

1/**
2* Insert content at caret position (converted to jquery function)
3* @link 
4http://alexking.org/blog/2003/06/02/inserting-at-the-cursor-using-javascript
5*/
6$.fn.insertAtCaret = function(myValue) {
7    return this.each(function() {
8        //IE support
9        if (document.selection) {
10            this.focus();
11            sel = document.selection.createRange();
12            sel.text = myValue;
13            this.focus();
14        }
15        //MOZILLA/NETSCAPE support
16        else if (this.selectionStart || this.selectionStart == '0') {
17            var startPos = this.selectionStart;
18            var endPos = this.selectionEnd;
19            var scrollTop = this.scrollTop;
20            this.value = this.value.substring(0, startPos)
21                                      + myValue
22                              + this.value.substring(endPos, this.value.length);
23            this.focus();
24            this.selectionStart = startPos + myValue.length;
25            this.selectionEnd = startPos + myValue.length;
26            this.scrollTop = scrollTop;
27        } else {
28            this.value += myValue;
29            this.focus();
30        }
31    });
32
33};