i really need help for this one:

A B C
oct 27 -50 cover
oct 27 -50 not cover
oct 27 50 cover
oct 28 150 cover
oct 28 -100 cover
oct 29 -50 cover

in this case, i need the number of "cover" from oct 27 to oct 29 that falls
under -50 only. is there any way to make it easier for me to get the number
of it? please help me..i will appreciate it a lot..thanks in advance