AFAIK, Ctrl+Alt+something is used in various layouts to produce extended characters, while Ctrl+Shift shortcuts are supposed to be reserved for the user (though many programs define shortcuts with Ctrl+Shift). Just plain Ctrl would be best. Normally AltGr+char shouldn't trigger a shortcut at all when focus is in a textbox (then again, some versions of Delphi had this problem as well, and you had to change something in registry if you wanted to type [] without switching keyboard layout).