Hi Lefrai,
I'm not sure whether I can help you at all. First I don't know if diffrent character sets like cyrilic are supported by Mach3, second if I could help you, it would only with Machscreen. The following procedure assumes the language setting english.
If you would use MachScreen, create a new screen and add a button. Be sure the button is selected and doubleclick in the line of "text on control" the string "text" (the background color changes to blue) and write your text in cyrilic.
Klaus