can you share with me a little more.
Like how?
My web app is on a plain IIS 6.0 web server it is a .net web app. (this is not a sharepoint server, just an iis server)
My k2 blackpearl is on another server in the same domain.
I think what Peter is suggesting is to add code in the page load of the page specified in the URL. You will use the SourceCode.Workflow.Client API. Details can be found in the K2 Help file or sample code from blackmarket.
As previously said in this post, you will need to have the code in the page load. Refer to the following link that connects to a K2 server, sets data field values on the process and starts an instance of a process.
http://help.k2.com/en/k2blackpointdevref.aspx?page=Start_Instance_and_Get_Data_Fields.html
Another thing to consider is the IIS AppPool account of your aspx page must have Impersonate rights on the K2 Server.