Event Subscription API: Filter to be triggered on any task change within a portfolio or program

Hello,

I have a question concerning the Event Subscription API of Workfront.

Is it somehow possible to create a new event subscription, which is triggered, if a specific value within any task within a portfolio or program is updated?

I know about the filter function, but as far as I understood, I am only able to provide an objId to limit the trigger to a specific task, or set it up for all tasks.

Thanks in advance.

Regards

Lars