Na cosa del genere?
codice:
<html>
<head>
<title>Titolo</title>
</head>
<body>
<script>
function Controllo1()
{
if (document.FORM.campo1.value == "")
alert("Riempire il campo1")
}
function Controllo2()
{
if (document.FORM.campo2.value == "")
alert("Riempire il campo2")
}
</script>
<form name="FORM">
<input type=text name="campo1">
<input type=text name="campo2">
<input type=button value="Button1" onclick="Controllo1()">
<input type=button value="Button2" onclick="Controllo2()">
</form>
</body>
</html>