Hola
sol1970
Prueba este ejemplo a ver si te sirve:
Código PHP:
<html>
<head>
<script type="text/javascript">
function anadir(obj,num) {
obj.selectedIndex+=num;
document.forms[0]['menos'].disabled = (obj.selectedIndex==0);
document.forms[0]['mas'].disabled = (obj.selectedIndex==obj.options.length-1);
}
</script>
</head>
<body>
<form>
<select name="sel">
<option>Uno</option>
<option>Dos</option>
<option>Tres</option>
</select>
<input type="button" name="menos" value="<" onclick="anadir(sel,-1)" disabled="disabled" />
<input type="button" name="mas" value=">" onclick="anadir(sel,1)"/>
</form>
</body>
</html>
Saludos,
