Create Excel Based Addon

The project is aiming to deliver an excel based addon with user management/profiles/accessability, to output xml, and connect to a secure website using SOAP. This requires a competant programmer with experience of working with excel addons, user profiles/management, xml, using industry best practice for user experience (UX). This is an Excel 2003 Addon, using Office standard libraries. Once this is complete, there will be another project to create a .net or windows xp application capable of similar, and probably more advanced functionality. I am also looking to develop into both projects, a user-licence based subscription package, which involves need for embedding activation code(s).