Remove Document from DocuSign Envelope using API from C#.net site

We are using DocuSign API on our website to send out documents to be signed. We send these documents in 'envelopes' with multiple documents in an envelope. We need a way to remove a single document from an envelope through the API. Project details are below: 1. After a user sends out documents for E-Signature the status on our website will be 'E-Sign Pending' 2. Under 'Action' the admin can select 'Undo E-Sign Request.' When they choose this we need code written that will remove the individual document from the 'envelope' in DocuSign. The other documents will remain in the envelope. If any user has already signed that signature will be deleted. 3. Our site is built in C#.net and is using the DocuSign API to currently send out documents. For those interested I can share a link to the website and show you the file and code that needs to be edited.