<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1251" />
<script type='text/javascript' src='http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js'></script>
<script type="text/javascript">
function func ( obj ){
obj.value++;
$('div').text(obj.value)
}
</script>
<title>Calculate</title>
</head>
<body>
<form id="for">
<input name="" type="button" value="1" onclick="func(this);return false" /><br>
<input name="" type="button" value="2" onclick="func(this);return false" /><br>
<input name="" type="button" value="3" onclick="func(this);return false" /><br>
</form>
<div></div>
</body>
</html>
Заместо func(this.value);