i really need help for this one:
A B C
oct. 27 -50% cover
oct. 27 -50% not cover
oct. 27 50% cover
oct. 28 100% cover
oct. 28 -150% cover
oct. 29 -50% cover

i would like to return a value where i only need the number of "cover" from
oct. 27 to oct. 29 that is under -50%...is there any formula so that i can
easily get the total number of "cover" at -50%