My question is this Can I say create a Osc with setting that I want which i know how to do But can i say route it to the computer keyboard say trigger it by pressing the letter A

Yes, you can. This is quite easy. First thing to do would be to have a look at kb.ck in the /examples/hid/ folder, this will teach you how to use the keyboard as a input device. Run that, press the key you'd like to use and see what id it has. You then include a shred that reads from the keyboard like that file does, write some rules to detect the keys you are interested in and link those to commands like;

if(msg.which == my_keynumber) my_envelope.keyOn;

Quite easy once you get the hang of it.

or can I just setup a char. variable to trigger it?

I don't quite understand this question, could you re-phrase it? What do you mean by "char. variable"?

Yours,
Kas.