void LimitText( int nChars = 0 );
nChars
Specifies the length (in bytes) of the text that the user can enter. If this parameter is 0, the text length is set to 65,535 bytes. This is the default behavior.
Limits the length of the text that the user may enter into an edit control.
LimitText only limits the text the user can enter. It has no effect on any text already in the edit control when the message is sent, nor does it affect the length of the text copied to the edit control by the SetWindowText member function in CWnd.
CWnd::SetWindowText, EM_LIMITTEXT