=SUM(IF(B2:B200="",A2:A200, B2:B200))

which is an array formula, it should be committed with Ctrl-Shift-Enter, not
just Enter.
Excel will automatically enclose the formula in braces (curly brackets), do
not try to do this manually.
When editing the formula, it must again be array-entered.

--
HTH

Bob

(there's no email, no snail mail, but somewhere should be gmail in my addy)

"nikko" wrote in message
...
Hi, pls advise if there's any formulas that can help to derive below

($) Sales Forecast, Estimate Rev, Actual Rev
Sales Off 1 - Jan
Sales Off 1 - Feb
Sales Off 2 - Jan
SAles Off 2 - Feb
Sales Off 3 - Jan
Sales Off 3 - Feb

I'm trying to sum-up the Jan, Feb and Mar data for All sales offices by
using the Actual Rev. If Actual Rev is blank, then use estimated Rev. If
estimated rev is blank, then use sales forecast nos.

Any help will be appreciated.. thanks!

--
nikko