Play mc backwards AS3

Flash friends:
I placed on the stage a movie clip that displays text.
There are left and right buttons on each side of the movie clip.
When the user clicks the button on the right the movie clip plays(); sliding the word out and revealing a new word.

I need to code the left button, so that when the user clicks it the movie clip plays in reverse sliding the text back to the last word.

I’ve seen and unsuccessfully tried a lot of code using prevFrame, but that function only moves the play head one frame.

Could anybody help me please.
How can code the left button so that it plays the movieclip backwards using action script 3?