a yase es asi?
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Pagina nueva 1</title>
</head>
<body>
<form method="POST" action="función fnc(f) {
f.action = 'www.especialidadesmedicaselite.com/descargar.php?file=' + f.campo.value;
}">
<p><input type="text" name="T1" size="20"><input type="submit" value="Enviar" name="B1"><input type="reset" value="Restablecer" name="B2"></p>
</form>
</body>
</html>