Text box Validation in MFC

I have 3 module name A, B and C in MFC dialog based application.
Each module has many text boxes. Some have same like username.
If I want to enter the alpha character as i/p.
But I need to validate three module text box in one common class using baseclass credit.
How to do?
Ex: A-usrTxt, B-usrText and C-usrText
If I use the common global box to automatically detect the textbox and proper validation.
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