excel - Summing rows condition on two columns -

i'd use array function conditional sum based on 2 columns. given example, each id want calculate sum of value column if column b -1.

  id  | b |  value | ________________________ 1 a1   1      2 2 a2   1      3 3 a3   1      4 4 a3  -1      5 5 a3  -1      1 6 a2   1      5 7 a1   1      1 8 a2  -1      2 

the outcome should be:

      id  |  value_total | ________________________ 1 a1   1      0 2 a2   1      2 3 a3   1      6 

this gives outcome show example data:

edit seems have ‘done trick’, explanation:

=sumifs syntax

sumifs(sum_range, criteria_range1, criteria1, [criteria_range2, criteria2], ...)

so in case formula summing columnd values in corresponding row columnb value whatever happens in columnb row containing formula , columnc value -1.

the answer not repeat column unique values of id because 3 distinct ids shown in example and, conveniently, these first 3 , in order.