Inventory.asp and update_inventory.asp -- just examples.
in inventory.asp at the very top of the page
-------------------
<%@language=vbscript%>
<%response.expires=0%>
--- Query the database ---
<%
dim oConn,strConn,oRS,strSQL
set oConn = server.createobject("ADODB.Connection"

strConn = "whatever you prefer"
oConn.open(strConn)
strSQL = "Select some_field from some_table"
set oRS = oConn.execute(strSQL)
%>
----------------------------------------------------
--- wherever your form is ---
----------------------------------------------------
<form name="invent" action="update_inventory.asp">
--- Populate the listbox ---
<select>
<%
oRS.movefirst
do while not oRS.eof
%>
<option value='<%=oRS("some_field"

%>'><%=oRS("some_field"

%>
<%
oRS.movenext
loop
%>
</select>
<input type="text" name="smth">
<input type="text" name="smth1">
<input type="text" name="smth2">
<input type="submit">
</form>
---------------------------------------------
in the update_inventory.asp at the very top of the page
---------------------------------------------
<%@language=vbscript%>
<%response.buffer=true%>
--- update or insert new data into the table, using response.form("smth"

values ---
--- then redirect to the previous page ---
<%response.redirect "inventory.asp"%>
The update_inventory should not have any HTML in order not to be displayed and run behind the scene, or it could provide some validation or confirmation. In that case, it has to be displayed with some navigation elements to the inventory.asp
The inventory.asp will requery database every time it's called.
This is just a schema and implementation is up to you...