It is possible. Drag a Server Event into the activity and follow any approach you find on the web

e.g.
http://stackoverflow.com/questions/11120452/run-powershell-script-from-c-sharp-application
http://stackoverflow.com/questions/7917873/calling-powershell-from-c-sharp-and-handling-exception

I know this is a really old post but I need to call a batch file or run a command from a workflow. using K2 Studio 4.7 I cannot seem to add code to a server event. My batch file calls an access DB that runs a macro and I really need to so this from the workflow ebcause the workflow gets attachements from an email, palces them on a file server and the access DB imports them into SQL. I omyl wrote the K2 side so rebuilding the access side would be hugely difficult.

Any help appreciated.