arrays - Sum based on values in other cells -

i have table in excel 1 below

date        |  type      |  value ---------------------------------- 21/01/2012  |  other     |  1000 22/02/2012  |  existing  |  1000 23/01/2012  |  existing  |  1000 24/01/2012  |  other     |  1000 12/02/2012  |  other     |  1000 13/02/2012  |  existing  |  1000 16/02/2012  |  other     |  1000 19/01/2012  |  other     |  1000 

i want formula add values of existing client each month example 1000 january existing , 300 january other.

i have tried know how can't seem make work.

 =sumifs(p2:p74,n2:n74,">="&n13,n2:n74,"<="&n43,o2:o74,"other") 

where n13 first , n43 last day of month, p value range , o column witho other /existing.