Hiya! Very Simple Help Needed For Actionscripting! (It's holding me back! =>_<=)

Hiya Im making a game in flash. I produce a lot games in the past but never messed with a java-like script in flash. My problem is Im making my character walk but the problem is when he runs while your press the arrow key I don’t know how to change the animation sequence when your not pressing the arrow key. So what im asking is I need to find a negate script (something that tells flash when this is not happenning is to do this) so I cant have my character go back to his netrual animation while he is not moving.

Here’s my code:

[color=blue]onClipEvent (enterFrame) {[/color]
[color=blue] [color=red]if (Key.isDown(Key.RIGHT)) {
} else if (Key.isDown(Key.LEFT)) {
[color=black]first the character is a movie clip inside this movie clip are 4 frames one with a movie clip in each some the first two frames are netruel position and the next 2 frames are running positions so ok just look at the code in red. I put when key is down “right”, Make character move and go to frame 3. the problem is now I dont have an script to negat the action so for flash to check when key is not pressed to go back to frame one.[/color]

This should be very easy to answer if anybody can help me to solve this all i can do is animation im not a very good proggammer but pretty much know how to make a game though. Thanx for your time for reading.