=INDEX(LINEST(F17:N17,F16:N16^{1;2;3}),1)

The above formula is part of a much longer formula.

I want to repace the references with the INDIRECT function but I am getting
#REF when I put INDIRECT in as the second argument.

=INDEX(LINEST(INDIRECT(S14),$F$16:$N$16^{1;2;3}),1 ) works fine.

=INDEX(LINEST(INDIRECT(S14),INDIRECT($S$15)^{1;2;3 }),1) when
S15="$F$16:$N$16"
and
=INDEX(LINEST(INDIRECT(S14),INDIRECT($S$15)),1) when S15="$F$16:$N$16^{1;2;3}"
both give #REF

How can I make this work? The Reference size changes depending on input data
set size so I figure I must use INDIRECT. It obviously does not like the
^{1;2;3} array formula part.

Thanks