Problem (from the German MS-Excel-Newsgroup of 2007/04/17):

        A     B        C       D  
  1 Customer Value                
  2    C      1                   
  3    A      2                   
  4    B      3                   
  5    B      4                   
  6    A      5                   
  7    C      6                   
  8    A      7                   
  9    C      8                   
 10    B      9                   
 11    A     10                   
 12               The last:     3 
 13 Sum:     22   for Customer: A 

Solution (Klaus "Perry" Pago of 2007/04/17):

B13: =SUMPRODUCT(N(OFFSET(B2,LARGE((A2:A11=$D$13)*ROW(INDIRECT("1:"&ROWS(A2:A11))),ROW(INDIRECT("1:"&$D$12)))-1,)))

Note: This works also with SUM, AVERAGE and other statistical functions of the same ranking, like MAX, when entered as an array formula (Ctrl-Shift-Enter). 

Comment: Klaus found a formula which orients on the cells, not on its contents, which often is complicated and thus very useful!

Using SMALL, you reach the first 3 entries instead of the last. By varying ROW(INDIRECT("1:"&D12)) you reach any other desired position.