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Excel/updating a cells value


i have a cell, A1, that has a formula that counts the number of tshirts i sell by using unique barcodes, and gives me a number. i have a cell, B1, that reflects the number of tshirts i had before i sold any, i need to update the value of B1 to reflect the subtraction of the thirts i sold. so if i have 10 in B1, i need it to automatically subtract the 3 from A1. A1 will change and i need B1 to change every time A1 does. how can i do that? normally in python or c++ i could do a += operand but that does not work here. any help?

I don't know python or c++ so that analogy didn't help me.
I don't get where the "3" came from in "automatically subtract the 3 from A1". Is it always 3? If so, then in B1 all you need is =A1-3.
Otherwise, I'm not following what you'd want to see in B1. Can you give more details?

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Bob Umlas


I`m a Microsoft Excel MVP (Most Valuable Professional) and have been since the inception of the program in 1995. I can answer every kind of Excel question except: API, Importing/exporting to other programs (powerpoint, word,...) Also check out my in-person training link at


Worked with MS Excel since version 0.99 (on the Mac!). Was contributing editor to Excellence Magazine, having written >300 articles. John Walkenbach said of me "I finally met someone who knows as much about Excel as I do."

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BA in math, Hofstra University, 1965

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Led sessions for the Convergence 2004-2006 seminar on Excel tips & tricks

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