Require last non zero values corresponding sl no in case of multiple entries.

My column "A" has SL.NOs, column "B" has a set of values recorded by my machinery, which are random and generally start and end with a zero.
I can find the last non zero value of my column B using the lookup function as
=LOOKUP(9.99e+307,1/ (B10:B1000<>0),B10:B1000)
my range starts from 10^th row and has 1000 values.
But, in case the last non zero value in column B is 5, occuring at, say 895^th sl.no and this happens to occur multiple times randomly, say at 200th, 318^th, 815^th positions in column B,
how do I return the sl.no correspunding to it's last occurence (i.e.) the value as 895?

Urgent help required!! Need it for my project!!