please help with a function that I am unfamiliar with.

say a1=1 and b1= "=a1*2"

I then want a3, a4 and a5 to be 2, 3, 4 respectively, and
I want b3, b4, and b5 to be the b1 function above where
instead of a1 it would be a3, a4, a5 etc.... without
having to repoduce the equation in b3, b4, b5 and still
get the right answer.

i.e. In B3 I want to be able to write "if my input is A3,
into the equation written in b1, then my answer would
be ..."

Basically I have designed a formula that involves various
tabs, and I cant compress it into one cell to crunch 100
different inputs, and I want to be able to compare all
the different answers at the same time.

Thanks for the help.