>The second texbox value is:
>

>iif( COLUMN3, "", COLUMN1)
>

>
>Depending on the value in COLUMN3, only one textbox is printed.

Acually, they are both printed, except one has "". But with PrintWhen you can control other things too - not just textboxes: lines, images etc.
Imagine that instead of one being bold, it had a border. You'd still see the border, as both would be printed, one empty (with border) and the other with column1 and no border. I'm not even sure how this would look, would one of them cause a newline or not.

To me it looks simpler to have a simple field value in each, then in one's PrintWhen you have "column3", in the other's "not column3".

Disclaimer: between 2006 and now I used fox reports maybe 20 times.