How to use Lookup formula for new rows in Google Sheets submitted via Google Form?

I am using the following Lookup formula in a Google Sheet: =LOOKUP(F2, AreaCodes)

I need that formula to be triggered when new rows are added via a Google Form.

I'm guessing the solution has something to do with ArrayFormula but when I try using =ArrayFormula(LOOKUP(F2, AreaCodes)) the values are not retrieved as new rows are added.