The following works for me in 4.1.
Set Infile `Requestfile TITLE "Input"`
Set Outfile `Requestfile TITLE "Output"`
Set Confirm `RequestChoice TITLE "Confirm" Body "$Infile*n$Outfile" "Quit"`
Echo $Confirm
(The last line is just to verify the RequestChoice worked as expected.)
I would expect that it would also work in 3.x, but of course I can't guarantee it.
Still, maybe it can inspire some new attempts.
Best regards,
Niels