Turn off Lg Chocolate Touch alert sound for text msg!?

I have the chocolate touch and compared to my older phones where i could go into sound settings and for the alert sound for a message i could simply choose none i cant do that with this phone and theres no way for me to turn JUST the text volume down. basically i want to know how do I keep my ringtone for calls loud but have no sound for a text message but still vibrate so i know i have one :D thanks