Asp coding: why it insert several time the same info into the table of database

Hello, I have asp code for login page. And if the username and password is correct, I want to insert into the caporder table the correspondent values in the specific column. But now when I run once the code, it insert into several columns of the caporder table with the same value if the username and password are correct. Could any one suggest how to modify the code? Thanks!

              
<%
set conn=Server.CreateObject("ADODB.Connection") 
conn.Open "Project"
dim username
username=Request.Form("user")
password=Request.Form("pass")
result=true

set rs = Server.CreateObject("ADODB.recordset")
sql="select username, password from customer"
rs.Open sql, conn
do until rs.EOF
  for each x in rs.Fields
    if username=x.value then
      z=true 
    end if
    if z=true then
      if password=x.value then
                  session("ID")=username
		
conn.Execute "UPDATE Capproduct set cus_id='"&session("ID")&"' where ID='"&session("idnumber")&"' and sid='"&session.sessionid&"'"  			
conn.Execute "INSERT INTO Caporder VALUES ('"&session("ID")&"','"&session("idnumber")&"',getdate(),0,0,0,0,0,0,NULL,0,0)"----insert several times in caporder

			Response.Write "<script>window.location='shipping.asp'</script>"
else result=false 
       end if
    end if
  next
  rs.MoveNext
loop  

rs.Close
conn.close

if result=false then
%>
              <script type="text/javascript">
alert("The username and password are not matched, please type again! ");
</script>
              <%
end if %>
              <form name="form" method="post" action="login_after_cap.asp">
                <p><font color="#0066FF" size="2" face="Verdana, Arial, Helvetica, sans-serif"><strong>Username: 
                  </strong></font> 
                  <input type="text" name="user">
                </p>
                <p> <font color="#0066FF" size="2" face="Verdana, Arial, Helvetica, sans-serif"><strong> 
                  Password: </strong></font> 
                  <input type="password" name="pass">
                </p>
                <input name="Submit" type="submit" value="login">
                <input type="reset" name="Cancel" value="Clear">
              </form>