i am devolping text to speech application in C#(windows Form Application).

i have done like :

SpVoice sp = new SpVoice();
sp.Speak(textBox1.Text, SpeechVoiceSpeakFlags.SVSFDefault);

but i need 2 types of voice for user to choose like
1.American voice
2.British voice

Any idea about how to do this..?
Thanking you.