How do I automatically change letters to other letters in a text editor?

Hi everyone. I am new to AutoIt and I like the program but I don't know how to use it. I work with languages and I would like to know how to change letters to other letters automatically in a word editor. For example, when the script comes across the letter д it will turn it into letter d. (transliteration)

Is this possible, and if so how do I do it?

Thanks.