Workflow item only to be completed from the Portal

[Tim Price]

Hello,

System ECC6 and Portal

I have developed a bespoke workflow that has workflow tasks calling a web dynpro. 
These workflow task call method DISPLAY on business object WEBSERVICE, this all works well. The tasks do not have Confirm end of processing checked.

I was wondering, if it is possible to distinguish if the task has been process/completed directly in R/3 without using the Portal to execute the task, as the business only want the tasks to be processed from the Portal.

Regards
Tim