Ideally I would like to do some sort of formula if the value cancels
eachother out for example -1 and 1 the result is zero but if the
values are not an exact negetive and positive match then it gives me
the actual values such as with ghi.

Or is there a neg/pos match, percentage or sumif I may do?

Excel Sheet
number proc amt
1 abc 1
1 abc -1
2 def 2
2 def -2
3 ghi 3
3 ghi -3
3 abc 4
3 ghi 3.5

Pivot Table
Row Labels Sum of amt
1 0
abc 0
2 0
def 0
3 7.5
abc 4
ghi 3.5
Grand Total 7.5

Thank you,
Mary