ASP.Net Code to find location of Library Document

Hi,

I am attempting to write a custom email extension to Sage CRM 7.2 for the Docusign API. The idea is that from a document in CRM you can then select to send this to a recipient, to do this I am writing a custom .Net dll. The issue I have run into is that I am not sure what the best way to retrieve the url for a document is. I know that I can get the location in the library of the document from the library record, however this will not create a url which I can use from an external location to return the document.

Does anyone know a way in which I can get the url of a document from within the CRM?

Thanks