a ver si te funca:
<!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=iso-8859-1" />
<title>Untitled Document</title>
<script language="javascript">
function lineas(obj){
var linea = document.getElementById("lineas");
var cant = obj.value;
var codigo = '<table width="100%" border="0" cellspacing="0" cellpadding="0">\n';
for(var i=1;i<=cant;i++){
codigo += '<tr>\n<td class="datos">Titulacion<br>\n<input type="text" name="titulacion'+i+'" size = "35"></td>\n<td class="datos">Nº Expediente<br>\n<input type="text" name="expediente'+i+'" ></td>\n</tr>\n'
}
codigo += '</table>';
linea.innerHTML = codigo;
}
</script>
</head>
<body>
<label for="select"></label>
<select name="select" id="select" onchange="lineas(this);">
<option value=""></option>
<%for i = 1 to 5%>
<option value="<%=i%>"><%=i%></option>
<%next%>
</select>
<div id="lineas">
</div>
</body>
</html>