how to receive values from a calling dll function

I want to receive values back from a calling dll function?

How do I do this?

This is the 'ASP' code I am using

<% @Language = "VBScript" %>
<% Response.buffer = true %>

<%
Dim Msg
Dim Lat
Dim Lon
Dim Map

Msg = Maps & "," & Lon &"," & Lat

' Lat=Request.QueryString("Lat")
' Lon=Request.QueryString("Lon")
' Map=Request.QueryString("Map")

Map = "OS2000.Map"

userid="1"

Lat = "50.748867"
Lon = "-001.554733"

Dim finalm

Set finalm = Server.CreateObject("DLLCall.Geomanconv")

RetStr=finalm.GEOMANCODE(Lat,Lon,Map)

%>

<%="Res="&RetStr%>