I'm using the Index and Match functions to return the month where inventory
levels for different parts run out based on changing forecasted usage. Based
on other discussions in this forum I was able to use the formula below, and
it works great, with one problem: my date ranges are January 2009 to December
2010. With my current formula, if the inventory level runs out before Dec.
'09, the formula will always return December 2010 (example, if inventory
value hits zero in Sept. 2009, the formula will return December 2010; if it
hits zero April 2010, it will return April 2010). What am I missing?

=INDEX($B$1:$Y$1,MATCH(TRUE,B2:Y20,1))

This is a sample of how my data is set up:

Jan-09 Feb-09 Mar-09 Apr-09
Part A 1212 852 421 0
Part B 52 0 0 0
Part C 3524 1254 0 0