Google Calendar OAuth integration with asp.net site

I have an asp.net application.

The asp.net application will allow users to subscribe to the system and authorise access to their Google calendars (one each)

An administrative function will then be allowed to update these calendars via the website on an arbitrary basis.

What I need is the OAuth side of things written. When a user signs up to my site I need them to be taken through the OAuth protocol and for them to provide my website with an Access token which will then be converted into a permanent access token (for seamless Calendar integration)

For those familiar with the OAuth protocol you will already know the process but in addition there are a couple of other points to note.

The ASP.NET application will not be registered with Google so HMAC-SHA1 must be used to create the signed signature for the initial unauthorised request token .

The final outcome must be an exchange of the user granted access token into a “permanent token” so that the ASP.NET application can communicate with the given calendar without any future user intervention

I am fairly certain that this could be written as a simple class and supplied in a .cs file but if any external library files were to be used then I would need the full code in order to make future modifications in the event that the OAuth standard changes.

If bidding, please can you be very specific about what you will supply (ie. make sure I know you understand exactly what is required in terms of the OAuth protocol)

I have seen some crazy bids on this site for insanely complicated projects with hardly any spec. Please don\'t bid unless you know exactly what I need - UK developers, dont be afraid to bid, I have budget for the right person and proposal.