|re: "when i populate column b with the names, i want to be able to see the corresponding letters appear in column a for each name"|
The most efficient way would be to use VLOOKUP.
First, you need to create a table with each name and it's assigned letter someplace in your workbook. It can be in a different sheet, in hidden columns, etc.
1 Mary Smith P
2 Jo Hunter P
3 David Fort P
4 Jessica King O
5 Chris Comet O
6 Paul Duncan O
In Column A, where you want the letter to appear, use something like this and drag it down:
When you enter a name in Column B, VLOOKUP will look up the name in I1:I6 and pull the corresponding letter from J1:J6.
You should review the Excel Help file on VLOOKUP to get a better understanding of how it works.
To "hide" the #N/A errors you will get if there is no name (or a wrong name) in Column B, expand the formula to be:
This will put "" (nothing) in Column A if the value in Column B is not found in Column I.