=concatenate function won't work

edit

I don't understand what a "(fake) Numbers format code @" is. How do I determine this and what should I format the cell (C1) to?

Format Cells...>Numbers tab>List at the left under Category: Bottom item Text, if chosen, puts the @ into the format-code line. This doesn't realy format numbers, but tells the cell not to apply a recognition process to entered/edited characcter sequences, but to take and keep them literally.
Cells containing formulas for evaluation must recognize them as formulas first. Therefore these cells must be formatted to a true Numbers format, A new recognition may require in addition some marginal editing.

Got it. It works now. Thank you very, very much. I had no idea. Had never run into that before... Peter

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