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!

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nikko