Looking for Access 2000 Code(VB)

I have a table that looks like a mileage matrix; the first field is labeled as “key” and it is filled down with city names. The rest of the fields across are labeled as the cities in the “key” column, and they are filled down with a number that represents the mileage from the “key” city, to the field city. I want the user to choose two cities from a form, and the result in another field would be the mileage. I don’t know how to pull just the mileage from the table. I can send anyone that can help me the table. email marcial.rodriguez@state.nm.us