lookup data in excel

Hi,
I’m trying to craft a query in ms excel 2003 that will look return the values. What I want to accomplish is type in data and the output would be the one before it and the one after it.

For example, if i have the following info:
a1 = aaa
a2 = aba
a3 = aca
a4 = ada
…

I want to be able to type in an input box (or other) ‘aca’ and the output will be aba & ada.

I’m sure that this is possible and i have been working with Vlookup, but i just can’t seem to get it to work.

Any help would be appreciated.

tk