as Father_Parsley said, its quite easily possible

Just ignore the first two words of the string

And oh, make the first letter of the third sentence into upper char
Update: Try this on for size
code:
var str="John is doing his job which is to study!";
str = str.substring(str.indexOf("is")+3);
str = str.substring(0,1).toUpperCase() + str.substring(1);
Debug.Trace(str);
To test it out, go to
W3School's Tryit Editor 1.4 and use the following code
code:
<html>
<body>
<script type="text/javascript">
var str="John is doing his job which is to study!";
str = str.substring(str.indexOf("is")+3);
str = str.substring(0,1).toUpperCase() + str.substring(1)
document.write(str + "<br />");
</script>
</body>
</html>