Assuming in A1:L1 are real "1st of month" dates:
01-Jul-05, 01-Aug-05, 01-Sep-05, ...
and targets completed are in A2:L2 : 3,3,3,3 ...
Put in M1: =DATE(YEAR(TODAY()),MONTH(TODAY()),1)
Then with your formula in say, N1:
it'll will return the sum of targets in A2:D2, i.e.: 12