I am having difficulty creating a formula. My list has clients who has been
with a company for x number of months. Depending on how long they have been
clients, results how much discount they receive.

eg:

A B C D E
FIRST LAST MTHS MTHS PERCENTAGE
REGD
Joe Blog 19 5 5%
10 10%
15 12%
20 15%

Can anyone help me?

Many thanks,
Marty