How do i get excel to replace words from data imported from the net.

Here is the problem. I am using excel to fetch data from a flight timetable,
however, when it says "KL" for the flight number, i want it to correct
itself to "KLM". Also, when it says "BA", i want it to correct itself to
"BAW".

i.e. "KL7746" would automatically change to "KLM7746".


Thanks in advance !


Regards
Andrew