One way using SUMPRODUCT ..
(a) the amount of tasks i allocated to DJC in January
(b) the amount of tasks i allocated to DJC in January that are closed
Via reading the month #s returned in col B
(a):
=SUMPRODUCT((B3:B10=1)*(C3:C10="DJC"))
(b):
=SUMPRODUCT((B3:B10=1)*(C3:C10="DJC")*(D3

10="Closed"))
Perhaps more robust by specifying it as "month & year" & reading this
criteria from the dates in col A:
(a):
=SUMPRODUCT((TEXT(A3:A10,"mmmyy")="Jan07")*(C3:C10="DJC"))
(b):
=SUMPRODUCT((TEXT(A3:A10,"mmmyy")="Jan07")*(C3:C10="DJC")*(D3

10="Closed"))
Adapt the ranges to suit ..