I'd like to have Excel validate data in several layers.

I have 2 columns, 1 for entering Project and 1 for
entering subproject.
The cells in the first column should validate the project
against a list of allowed project. This is no problem, I
use the Validate function.
But, for the second column, I'd like to be able to chose
(in a combo box) from a list of subproject that belongs
only to the project I entered in the first cell.

"Valid list"
Project: Subproject:
A 100
A 110
B 200
B 210

If I chose "A" in the first cell, I'd like to be able to
chose and validate that only "100" or "110" can be used in
the second cell.

Can this be done in Excel without programming?

Thanks