questa è la pagina che ho usato come prova
codice:
<!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>
    <title>Pagina senza titolo</title>

    <script language="javascript" type="text/javascript">
// <!CDATA[

function ShowHide(e,id1,id2,id_se1) 
{
	//accedo all'oggetto event
	if(!e) var e = window.event;	
	
	var target = (e.target)?e.target:e.srcElement;
    if(target.tagName.toUpperCase() == "BUTTON" )
    {
        if(document.getElementById) 
        {
            el1 = document.getElementById(id1);
            el2 = document.getElementById(id2);
            se1 = document.getElementById(id_se1);
            if(el1.style.display == "none") 
            {
                el1.style.display = "block";
                el2.style.display = "none";
                se1.disabled = false;
            }
            else 
            {
                el1.style.display = "none";
                el2.style.display = "block";
                se1.disabled = true;
            }
        }
    }
    else if(target.tagName.toUpperCase() == "SELECT" )
    {
        var valore_select = target.value;
        document.getElementById("show1").disabled = valore_select != "";
    }
    
}

// ]]>
    </script>
</head>
<body>
    <select name="autore" id="autore" onchange="ShowHide(event);">
        <option value="">Seleziona Autore</option>
        <option value="1">Autore1</option>
        <option value="2">Autore2</option>
        <option value="3">Autore3</option>
    </select>
    <div id="show1">
        <button onclick="ShowHide(event,'show1','newfields1','autore');return(false)">Apri scheda</button>
    </div>
    <div id="newfields1" style="display: none">
        <button onclick="ShowHide(event, 'show1','newfields1','autore');return(false)">
            Chiudi scheda</button>
        Nome:
        <input type="text" name="nome_autore" />
        Cognome:
        <input type="text" name="cognome_autore" />
    </div>
</body>
</html>

Lo devi prendere come esempio da riadattare, se il caso