Lookup value in Column A, add text to Column K

Please accepy my apologies as a newbie if this is a relatively easy task, but I just havent cracked it yet.

I am trying to use vba code to lookup a value (ticket number) in column A, as selected by a user (via an input box) and if a match is found, add the word 'cancelled' in the corresponding cell in column K.

I have been searching on the web and have been trying to using the find fuction, but without any success yet.

Any help appreciated.