I have a table of data that tracks progress across time (down each
row), so that one column (B) will hold a dollar value that will
change. This value is going to serve as a benchmark, so that it is
persistant for some time, then changes as it has been met.

My problem is that I need some way to track these benchmarks as they
change so that I can easily refer to the last one that was populated.
If at some point in my table, I have values:

Row Col. B
..... .....
20 $5000
21 $5000
22 $5000
23 $5625

I want the value $5000 to be available in rows 23 and down. Is there
an easy way to do this? I'm afraid of complex worksheet or array
formulas, because I have so many rows of data (104,000+).

Any help would be great. Thanks in advance.