I need to be able to update a particular data field in a process (let's call it process A) from another process (process B).  In process B, I know the process instance ID for the process A that needs to be updated.  Is there a way to do this without using a Server Code Event that uses the API and/or SmartObjects?

I considered adding a reference to the Process Data SmartObject in process A, but there are other processes that need the same functionality.  In other words, process A could be updated from process B, process C, or process D.