Another Excel Question

[Vince, Pt. II]

Let's say I have the following column in excel:

A
211
212
210
209
...

The list will grow over time, and at the bottom of the list, I want a simple delta:

=a1-aX

Where aX is the last entry in the column. However, I want to make it so that the formula doesn't have to be updated every time I add a number to the bottom of the list. Is there a way to make a floating anchor like that, or am I going to have to find the value of the last non-empty cell and then reference that cell?

[Bobble]

You could count how many entries in the list with COUNT or COUNTA and then use OFFSET to "step" down to that number:

=A1-OFFSET(A1,COUNT(A:A)-1,0)