I want to perform a date calculation. For example:

a
1 date
2 2004-01-04
3 2004-01-11
4 2004-01-18

.....and so on. I'll continually add things to this column and the goal
of the calculation will be to determine how many days span between the
item in a2 (the first date) and the last date. The trick is "how do I
tell Excel that what should be subtracted is the bottom-most item?
Today it'll be a3 but next week it'll be a4, then a5, etc.

Help?

Of course, let me know if this isn't clear.

Also, is there a way in Excel to add descriptors without actually
having them be part of the calculation? For example, I have "date" in
cell a1 in the above example. That doesn't seem to be affecting
calculations such as =sum(a:a) but it still looks messy. Ideas?

Third, is there a way to hide the messy #DIV/0! errors? I've done
fill-downs for things that don't yet exist and so they're there.

Finally, is there a way to say, in Excel, "fill down from here?"
Because of the above, ugly text descriptors, I find myself having to
do things manually like "=sum(d1:d1000)", which seems kind of odd.

Thanks in advance for all the very-likely newbie questions,
Jason