What version of Excel are you using? In 2007 and later you could just use SumIfs.
=SUMIFS(M:M,B:B, "11_22", L:L, 303, M:M, ">=" & 1)
(Not entered as an array formula)
That'll be much simpler going forward.
To add your second criteria, just add two formulas together to make a longer formula...