=SOMASE([almox.xls]Sheet1!$C:$C;A2;[almox.xls]Sheet1!$H:$H)
I converted my formula to this one, as it pulls information without having to open the file, but it is not correctly adding up the balance of the items.
=INDEX('[snd.xls]Sheet1'!$H:$H; CORRESP(A2; '[snd.xls]Sheet1'!$C:$C; 0))
Example: if there are two lines in which the reference is the same but the balance is different, the formula does not add the two balances and shows it in the cell
