How can I create a series of pull down menus where the 2nd, 3rd and 4th tier
are based on the preceding choices?

I know how the validate command can work, but and not sure how to create a
dynamic way to populate to ensuing tiers based on the previous selection.

In short....you pulldown item 1, which determines what can be pulldowned
from item 2 and so on for 4 levels.

Now the real challenge is on top of this: I need to repeat this
independently about 200 times. So you will have 200 sets of pulldowns all of
which need to be populated.

Thanks