Conceptually it is certainly possible to do. Figuring out a method of teaming graphics to source info is going to be the trick.

I would set up the Powerpoint file so that graphics to be updated contain their own metadata that allows you to source the image. For instance, if you select a graphic in Powerpoint and go to Format Picture you can put text into the Alt Text and Description fields. I would use these fields to then tell the macro where to source the replacement graphic.

Word document structure and layout will be important - graphics in Word can be floating or inline so 'Image 3' could be interpreted in two different numbered collections.

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Andrew Lockton
Chrysalis Design, Melbourne Australia