ho una pagina asp che visualizza alcuni campi di un database

con un pulsante per modificare

i campi sono 7, ma da modificare solo 4.

quando faccio modifica, va tutto bene per due dei 4 campi, mentre 2 dei campi vengono svuotati, cioè viene salvato ""....

mi sembra molto strano

codice:
<%@LANGUAGE = VBScript%>
<%
if Session("Autenticato")<>"OK" then
	Response.Redirect("../index.html")
end if

act = request.querystring("act")

Dim cn, rs
Set cn = Server.CreateObject("ADODB.Connection")
cn.Open "driver={Microsoft Access Driver (*.mdb)};dbq=" & Server.MapPath("../../data/manage.mdb")
Set rs = Server.CreateObject("ADODB.Recordset")

if act = "salva" then
	rs.Open "SELECT * FROM fatture WHERE id = " & request.querystring("id"), cn, 3, 3
	rs("ft_acquisto") = request.form("ft_acquisto")
	rs("€_acquisto") = request.form("€_acquisto")
	rs("ft_trasporto") = request.form("ft_trasporto")
	rs("€_trasporto") = request.form("€_trasporto")
	
	rs.update
	rs.close
end if

rs.Open "SELECT * FROM fatture WHERE id = " & request.querystring("id"), cn, 1

tot_vendita = rs("prezzo") * rs("quantita")
guadagno = tot_vendita - rs("€_acquisto") - rs("€_trasporto")
%>

<html>
	<head>
		<title>Dettagli Camion</title>
	</head>
	<body>
		


		<% if act <>"modifica" then %>
			<form method="get">
				<input type="hidden" name="act" value="modifica">
				<input type="hidden" name="id" value="<%=rs("id")%>">
				<input type="submit" value="Modifica dati">
			</form>
		<% else %>
			<form method="post" action="details.asp?act=salva&id=<%=rs("id")%>">		
		<% end if %>
		<table border="1" width="58%">
			<tr bgcolor="00FFFF><td colspan="4"><h2>Dettagli camion</h2></td></tr>
			<% if rs("tipo") =  "commerciato" then %>
				<tr bgcolor="00FFFF">
					<td colspan="2"><h4>Acquisto</h4></td>
					<td colspan="2"><h4>Vendita</h4></td>
				</tr><tr>
					<td bgcolor="00FFFF" width="25%">Ft. acquisto</td>
					<td bgcolor = "CCFFFF" width="25%"><%
														if act <> "modifica" then
															response.write(rs("ft_acquisto")&"")
														else
															response.write("<input type=text name=ft_acquisto size=20 value=" & chr(34)&rs("ft_acquisto")&""&chr(34)& ">")			
														end if
														%></td>
					<td bgcolor="00FFFF" width="25">Ft. vendita</td>
					<td bgcolor = "CCFFFF" width="25%"><%=(rs("numero")&"")%></td>
				</tr><tr>
					<td bgcolor="00FFFF" width="25%">€ acquisto</td>
					<td bgcolor = "CCFFFF" width="25%"><%
														if act <> "modifica" then
															response.write(rs("€_acquisto")&"")
														else
															response.write("<input type=text name=€_acquisto size=20 value=" & chr(34)&rs("€_acquisto")&""&chr(34)& ">")							
														end if
														%></td>
					<td bgcolor="00FFFF" width="25">€ vendita</td>
					<td bgcolor = "CCFFFF" width="25%"><%=(tot_vendita)%></td>
				</tr><tr>
					<td colspan="4"></td>
				</tr><tr>
					<td bgcolor="00FFFF" colspan="2"><h4>Trasporto</h4></td>
					<td bgcolor="00FFFF" colspan="2"><h4>Guadagno</h4></td>
				</tr><tr>
					<td bgcolor="00FFFF" width="25%">Ft. trasporto</td>
					<td bgcolor = "CCFFFF" width="25%"><%
														if act <> "modifica" then
															response.write(rs("ft_trasporto")&"")
														else
															response.write("<input type=text name=ft_trasporto size=20 value=" & chr(34)&rs("ft_trasporto")&""&chr(34)& ">")															
														end if
														%></td>
					<td bgcolor = "CCFFFF" width="50%" colspan="2" rowspan="2"><h4><%=guadagno%></h4></td>
				</tr><tr>
					<td bgcolor="00FFFF" width="25">€ trasporto</td>
					<td bgcolor = "CCFFFF" width="25%"><%
														if act <> "modifica" then
															response.write(rs("€_trasporto")&"")
														else
															response.write("<input type=text name=€_trasporto size=20 value=" & chr(34)&rs("€_trasporto")&""&chr(34)& ">")		
														end if
														%></td>
				</tr>
		</table>
			<% if act = "modifica" then %>
				<input type=submit value=Salva >
				</form>
			<% else
			
			end if
		elseif rs("tipo") = "prodotto" then %>
		
		<% end if %>
	</body>
</html>

<%
rs.close
cn.close

set rs=nothing
set cn=nothing

%>