Summing Numbers With Specific Values To The Left Of Them

Hi guys im new here and I have a problem that if someone could help me with would make my job alot easier. At my work I am responsible for compiling a monthly report. Well I have to gather data from an Excel document and add up all the totals and then print them out. Well there are like 40+ worksheets and the (lets call them) items arent always in the same locations (along with the values) so i was wondering if anyone knows how i can sum up values from multiple spreads and can do so while still summing up each value that belongs to the same item. Ill attach a screenshot of what one of the worksheets looks like. And remember that not all of these things are in the same order as the other worksheets