Voice Recognition to control a Car?

Hey Guys, We are currently working on out project at the moments, on using voice to control the car to help people with disabilities have an easier task. We are currently processing signals, what we are stuck on is how to use the signals input and put them into code.. for talk sake, "turn left" the speech is processed and then has to be inserted into code, is this quite simple or a bit complicated? We will then filter it out. Thanks guys, suggestions and advice would be much appreciated.

[Walter Roberson]

This is speech recognition rather than voice recognition.

[Jason]

Thanks, I know there is a big difference, but yet again to filter out any noise before it goes into the GUI interface would it be difficult? Also will it only recognise the one voice or many others?