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LO, OS Mojave 10.14.6

I attempted to follow a tutorial on the subject on youtube (which is only a few minutes long- https://www.youtube.com/watch?v=6yZebrMBlBo); this tutorial serves not only as a guide but explains what I am trying to achieve more thoroughly/effectively than I can here.

Unfortunately the tutorial is for Excel, as I didn’t manage to find an equivalent for LO. As such, after following the tutorial I found my methodology lacking: the images didn’t change as intended. I sort of guessed at some of it, as I’m not hugely familiar with named ranges etc, and the layout/naming of menus etc. in Excel differ from those of LO.

I did notice that at the end of the video the author seems to name the “placeholder image” he mentions as “Pictures” (correct me if I’m wrong); I didn’t manage to do this, as when I select the image and try to name it in the (formula bar?) I get a “#REF” error in the cell containing the placeholder image- possibly a clue as to where I’ve gone wrong?

Anyway, here is the document in question- could someone please point out where I’ve gone wrong/amend the document to correct my mistake?

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