Excel 2007 : Populate a cell by formula OR by manually entering data?

I'm creating a simple database and I want to be able to populate cells in a column (let's call it USERS) either via a VLOOKUP formula based on entries in another column (USER NUMBERS), or by typing in data directly into the cell in the USERS column. And I want to retain the formula if users do the second method. Is this possible? I thought maybe I could create a third column (USER'S LOOKUP) and have it link to the USERS column, but that won't work. Or will it?

I would attach the workbook, but it contains personal information. If you need me to create a sample workbook, I can.

Any ideas would be appreciated.

Thanks, Bruce

I think you are confirming what I already knew. Let me see if I have it correctly. Here is the scenario:

I have a call log sheet. Column A lists names. Column B lists ID numbers associated with these names, both of which are stored in a list on a separate sheet.

I want users to be able to enter the name by typing it in directly into Col A (or by using a drop-down list), or by entering the ID number and having Col A auto populate.

You are saying I need a third column that will display the name if users enter the ID number because there is no way to have Col A populate by either direct input or by entering a number. Is that correct?