How do I lookup a value in say column and in returning the found

Hello,


How do I lookup a value in say column and in returning the found value replace the it with a typed value. An example is;

a b c
------------------------
q r
f f
e h
q w
r m

So I am looking for q in column A and if found return the found value q replaced with the

word "new". Instead of returning q I want it to return new in column C.

Your prompt input will be greatly appreciated.