I need to make a mass replace of one word to another word but I want to preserve the case.

Example I want to change TheOldWord to TheNewWord. But if the theoldword is this way then it needs to be thenewword or if is TheOLDWord it needs to be TheNEWWord or THEOLDWORD to THENEWWORD. I don't know all the cases that it might be in.

I was hoping to not have to use ATC to find the word then loop checking the case with isupper and islower functions.