Open Next WorkList using c# code

When you call the K2Item.Finish() method, you will have to finish it Synchronously:
K2Item.Finish(true);
This will force K2 Server to execute all the activities and rules until it hits a Async server event or a client event before passing focus back to the code that called the Finish method.

You can then open the user's Worklist again, filtering the items using the folio or process instance ID and redirect the user to the new page directly. There are a few posts on this I believe.

As per DC's suggestion, you can check out this previous forum post:

   http://k2underground.com/forums/post/13841.aspx

This provides an example of how to use K2 to direct web page navigation.