Excel 2010
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7a
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[TD="align: left"]=SUMPRODUCT(
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[TD="align: left"]{=SUM(
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Entered with Ctrl+Shift+Enter. If entered correctly, Excel will surround with curly braces {}.
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Your question indicated the numbers in Columns A and B.
Your statement that follows is not consistent with the initial question.
"I also filled in numbers in the proper rows and columns (Rows 3,6,9,12 - Columns 5,8,11,14) to check the calculations. Any thoughts on what I could be doing wrong?
Try submitting a concise example that reflects your challenge.
Is this question duplicated at
https://www.mrexcel.com/forum/excel-questions/1044560-sum-repeating-values.html#post5014950