"a" is replaced to "alpha greek symbol"

Dear sirs,

For viewing xml file on IE
We are getting non-keyboard characters through entity,character code
(unicode value) and also fonts.
Without using xsl, dtd, entity,character code(unicode) and fonts, how to
replace particular keyboard character to particular non-keyboard character.
(for example "a" is replaced to "alpha greek symbol  a" ) Could we use
customized encoding for particular xml file? If it is possible, how to do?

Thanking you

Regards
Baskaran NK