Is there a way for selections in a drop-down menu to generate different cell values?

Hey everyone, I'm new to the boards and only moderately familiar with Excel, so I'm looking for a little help. My question might not be completely clear, so I'll try to give you a visualization.

I want to give users the ability to choose different kinds of expenses from a drop down menu (i.e., Salary, Postage, Supplies). However, some of the expenses have general costs associated with them on top of other costs, and I want it to be made clear by having the proper costs come up with the proper expense. For example:

A
1 "Supplies" (is chosen from the drop-down)
2 "General Supplies" (automatically is generated)
3 Blank space for them to input a specific supply expense.

As opposed to:

B
1 "Salary" (is chosen from the drop-down)
2 Blank space for them to input a specific salary expense (because there is no general one associated with salary)

I have been able to do the first example using the Lookup function, but the problem is that the function is listed in the A2 cell where I would want a blank space if it was for Salary, for example.

Any ideas would be much appreciated. Hopefully that explanation was somewhat understandable!