joeu2004, I appreciate your reply! I like your suggestions, I guess
it made me re-think my question.

I suppose ultimately this is what I need to know:

If I have two datapoints, what formula/method can I use to get the
approximate linear values between them given a certain range of
cells. For example, if I have "100" in cell A1 and 1000 in cell A10,
but cells A3 to A9 are empty, what dragging/mouse clicks/formulas can
I use to "autofill" the empty 8 cells in between them?

In this case, the numbers being so straightforward, it's easy to say
A2 would have 200, A3 would have 300, etc. But if the numbers are
more complex, what could I do to get those values filled in assuming
it's linear? Meaning, I know my two end points, but don't know what's
in between-- I want a linear set of values calculated between them
based on the beginning and end values. Maybe this is a simple task in
excel?