Help with analysing data required..

I have a data set of 5000+ rows

From this I am trying to find out a relevant bit of data pertinent to both a subject and a date.

By way of explanation I have in

Column A - a variety of subjects
Column B - dates
Column C - values

A subject can have many dates

Essentially what I'm trying to achieve for a given subject and date is...

The value attaching for the largest date on or prior to the given date

So for example if, for the subject X and the date 31/12/96 applied to the following data set

X 1/10/95...20
X 14/2/96...15
X 30/6/96....18
X 29/9/96....17
X 14/7/97....22
X 28/6/01....25

I am trying to secure the return of the value 17.

Any help would be much appreciated

thanks

Sorry to bump this but I hope you don't mind me giving this one more exposure