Writing my own field using formula -

Hello again,

i would create my own field using a formula for my own report.

So i want to write : if "field" = "pippo" then ----ecc ecc

But "field" is not available from the list i see. How can i know  which is the correct name of the field i want to use for formula?

Let me know if u understand :s

Thank u

Giuliano Sciuto