Word did not insert the \* MERGEFORMAT switches as a result of applying anything in the tutorial. What's the point of the SKIPIF field in cell B1?

Done properly, your IF field code would look like:
{IF{=A1}= 330 "33x26x20" {IF{=A1}= 250 "25x22x15" "39x26x25"}}
You could even use a field coded as:
{=A1-250 \# "'33x26x20'; '39x26x25';'25x22x15'"}

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]