ctrl+v and ctrl+c shortcut keys not working in windows textbox

hi,
i created one textbox in windows application.This textbox allows only numeric values ,
and my problem is when i am trying to copy(ctrl+c) and  paste(ctrl+v) any text on  textbox it not alllowed.
i set shortcut property also true... still it's not woking..
plz give me any one solution.....