How to start an Other Program on arduino?

Hi ,
i have a simple program which is detect people in an area with a movement sensor , but , how can i made this program automaticaly start an Other program when a person is detected ?

Don't start another "program", start another function.

no , the arduino program should launch a program on processing

First mention of Processing. Why not just start another Processing function?

cause the program on processing should only start when the sensor has detected a person

OK, let's quit the "Twenty Questions" game, and find out what you want to do and with what resources. Despite the topic title, this is looking less and less like an Arduino question and more like a Processing question.

I just want to know , how can i start a processing program directly with my arduino program

I just want to know why you think that is the right thing to do, but I'm going to say "gobetweeno" instead.

I just want to know , how can i start a processing program directly with my arduino program

You can't. If the Processing program is ALREADY running, you can have the Arduino send serial data, and have the Processing sketch read serial data, to determine what to do,