Well…I opened this thread to help, but looks like you've already figure it out, so instead…congratulations on learning one of the Excel formulas that I use the most often!
Also, if this helps any, you can start to type any Excel formula into a cell and it will tell you what the part of it are. So, like, if you type “=SUMIF(“, it will display below where you're typing “SUMIF(range,criteria,[sum_range])”, which means a “SUMIF” is built by specifying a range (where to look), then you have a comma, then the criteria to look for in that range (what value you want to find cells in the range that are equal to it), then a comma, then the range that should be summed up. If you learn to interpret these Excel hints, it will help you decipher other people's workbooks when they use a formula you're not familiar with. 🙂 Just know that everything between commas counts in the formula you're looking at is part of the
The other confusing thing in this formula is the reference to other tabs – in this case, “TTB-2015”. Know that any time it references a cell and doesn't have a tab name in front of it, that means it's on the same page as the formula, which is why the CY10 was where you found it. Only cell names (like E7) or range (like E7:E4005) that have a sheet name in front of them can be on different sheets.
P. S.: I'm assuming you figured this out by now, but if not, now that you've said CY10 is an account number, the value yielded by the formula is the total amounts in column E of TTB-2015 for all the times that the specific account number shows up in column A of TTB-2015. So, if TTB-2015 lists the account number 10 times, then this formula gives you the total of all 10 times it's listed.
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