Kouakou,
If what you are trying to accomplish is to prevent backspace from taking you out of a textbox into the previous control (one of the most truly annoying things in VFP) is to put this code into your lowest level textbox subclass:
LPARAMETERS nKeyCode, nShiftAltCtrl
if ( ( m.nKeyCode = 127 ) and ( this.SelStart = 0 ) )
nodefault
endif
>how to deactivate the backspace key ?