how to use a button

i need help please!

i want to make an app so that i can control a car through my mobile

i'm using buttons and i want that when i'm pressing the button the car keeps going forward and when i take my hands off the button the car stops 

and if there is another way other than the button ,i'm very open minded

thanks in advance

Please do the tutorials first, and read my tips below.  The tutorials are located here: http://appinventor.mit.edu/explore/ai2/tutorials

For our App Inventor Tips, visit TwoDogApps.com

AI2 apps can only control outside devices using Bluetooth communication.

If you are trying to control Lego 'robots', you can use the LEGO NXT AI2 controls.    If you use arduino, you use bluetooth.  to find out more,

you could  SEARCH in the forum using the Search for topics box to the right of the colorful google at the top of this page   using terms likeLEGO or NXT or arduino or bluetooth  or search for app inventor plus LEGO or NXT or arduino or bluetooth  on the Web and find out a lot about controlling outside objects.

Really control an automobile?   Wow.    Might be possible using a small computer like an arduino hooked to switches, if that is your real question.