Lookup and Fill In

I have a field that must be populated with a certain value. It's a five digit figure and there are 250 of them. These are account numbers. These five digit account numbers roll up to a description and then up to a final rollup name. The rollup name is the highest level of this hierarchy.

There are five rollup names:
Construction
Furniture
Security
Noncapital
Contingency

Each of these has from 10 to 50 accounts asssociated with it.

I want to have users go into the Excel file and have a drop down list. The first one would have just the five rollup names. From this list they pick one. (Let's say they pick Construction).

After they pick the category (construction) they go to the cell to the immediate right. Another drop down list. This one contains all the descriptions and account numbers associated with the rollup name they picked for the first cell (construction). They need to pick one of these.

When they do this, the third cell (to the immediate right of the one they are currently on) is automatically populated by the five digit account number.

It is just a matter of narrowing the users choices down to a certain number and then having the account number autopopulate. I've tried VLOOKUP with a formula but it is not working. Anyone have any suggestions??