Sum if columns match in separate sheets and total from another column

[2k05gt]

I have been hurting my brain on this..
I have 3 sheets, 1 sheet "VARs" is a List of the items specs by Model Number, the column I need to sum is in this case weight in Lbs
Sheet 2 "Drive_List" is a List of items that have the same model number (S/N make the different) that are put into Boxes that are numbered
Sheet 3 is "Box Count" this is a count of how many items are in a box and how much it weights . Here is the issue.
How can I get a sum of all the items weight in each box. the weight of each item (model number) is different and each box has a mix of the items.

I tried using indexing, with offset but working with 3 different sheets got confusing, I defined names for each of the columns I was working with
but nothing would work.

Thanks in advance for any assistance

 

[2k05gt]

Ok...good. You can see the array in your diagnostics. Click on the cell with the formula, then go into the formula bar where the formula appears (click at the end of the formula), and re-confirm the entry by entering it with Ctrl-Shift-Enter, to enter the formula as an array formula. You should see curly brackets form around the expression. Alternatively, replace this dynamically formed array with a simple range reference to the helper cells in that row.

I totally forgot about the Ctrl-Shift Enter thing... that works

 

[KRice]

Yeah…that array needs to be created and then passed to SUMIF, so it needs to be an array formula in this case. The alternative idea that declares the full range reference of the helper cells should not require the CSE entry.