Find And Replace Certain Characters

I have some records that include greek addresses. The greek alphabet contains letters that are common to the english one (A,B,E,Z,H,I,K,M,N,O,P,T,Y,X) and records with mixed characters will cause me problem. What can I do to find and replace any of those letters with the greek version of the letter.

example:

for a record:

T.�.5123 (this is the Greek abbreviation for P.O.BOX 5123)

I'm looking for a function to replace the first letter T (wether is Greek or English) with the Greek version of it

example 2:

KYMH� 6 (kimis is the street, 6 the number)

I should replace English (first four ) letters with the Greek version...

example 3:

BA���PITOY 14 (valaoritou is the street, 14 the number) ...........