I think you're talking about minimizing the time it takes for VA to recognize voice input and act upon it so that you can speak two 'When I say' commands in close proximity and get them both to register.
One thing you can do is go into the Options and within the Recognition tab set the "Recognized Speech Delay" option to a lower value. This should reduce the time between VA recognizing a voice command and VA acting on that positive recognition.
SOME pause between spoken commands will be needed though, otherwise VA may think what you are saying is one spoken phrase (instead of two) or VA may only execute on one of the portions of your spoken phrase.