Active Directory 2 Factor Authentication System

We require software that will run on a Windows server to provide two factor authentication for a user. A user will log in with their username and password which will authenticate with Active directory. The security will be further enhanced by the user having to enter additional details. This additional information will be sent to the user via an email that they will receive on their phone and then enter the details to confirm who they are forming the 2nd factor of authentication. We are not after a finished product but more a proof of concept. A virtual server will be setup to allow the developer to setup the test environment. No milestones will be paid unless the proof of concept works. We are not after a high quality looking solution to start with. Additional funds will be paid to further enhance the solution at a later stage should the software delivered be of high standard.