Help with =CHOOSE()

[Jean-Michel]

Thanks Tim And Tyann for your prompt reply, but unfortunately I still cannot have it functioning.
I tried again by having the CHOOSE function pointing to another cell (as first argument) than the one where it is, but no way. Same with replacing the cells references by a list {10 20 30}.
Might this be RPN sensible?

EDIT: switching to BOOK entry mode makes it work flawlessly.

So, following question: is it possible to have it functioning in RPN mode?

{2nd EDIT: it seems that one has to be in BOOK mode at the times you enter the equation. Switching back to RPN has no detrimental effect once the equation is entered}