What I have up to now:
- in separate ppt file: insert either a pie chart or a Partial Circle shape
- in original ppt file: insert object 'from file' >> add animation OLE Action Verbs > Edit (with trigger to click on the object)

This way when clicking the object in Slide Show View the separate ppt file opens and can be edited.

Unfortunately this is too complicated for the target users. They want to be able to update chart data (or partial circle) in the original Slide Show.

Any thoughts?
Thanks!