The onSelect event handler is fired when the text in the box is highlighted.
<html> <head> <script language="JavaScript"> <!-- function setText(){ document.myForm.myText2.value = document.myForm.myText1.defaultValue; } --> </script> </head> <body> <form name="myForm"> <input type=TEXT value="Change Me?" name="myText1" onSelect='setText()'> <br> <input type=TEXT value="" name="myText2"> </form> </body> </html>