Change adjacent cell depending on text

Hi all, this might have to be slightly vague, so please bear with me. I can provide more info if required.

(Excel 2003)

One of my many spreadsheets contains two columns, B and C.
Column C contains the name of a client.
Column B contains the name of an employee.

Each client is assigned a certain employee, and some employees look after multiple clients.
However, in the form that I receive the spreadsheet, some of the employee names are missing or incorrect, so I have to fill them in depending on the client.

EG: employee A looks after clients X and Z
Employee B looks after client Y

How can I make it so that column B (employee) is filled with the correct employee depending on the adjacent client in that row (column C?)

I was thinking something like an "if colC = "client X" then colB = "employeeA" but I know nothing about macros. If I get a generic macro with placeholder names I can fill it myself.

One catch: as I mentioned, some employees have one client, some have up to six.

Another catch: I do NOT want it to select row 1, as that is a header column and has filters applied.

Thanks in advance and sorry for the poor explanation, I will try to be as responsive as I can.