On the Palm platform there was an app called "Key Caps." What it did was allow you to quickly hit a key twice in succession and it would generate a capital letter (hit "g" twice quickly on the keyboard and it would turn it into a capital G" or if you held down the key for a second, it would generate the ALT symbol associated with that key (a "%" for the "g" in this case). The prefs menu allowed you to switch those (i.e. double-tap and get the ALT, hold down long and get the capital). Any chance of doing something like that?