onEnterFrame Help

how to recall a onEnterframe action
My movie clip moving to left onEnterFrame and i created a button to stop on onRollOver with "delet this.onEnterFrame" function but i need the movie clip scroll again on onRollOut. can anybody help me .

my_clip.onEnterFrame = function() {

this._x+= -2;

btn.onRollOver = function() {
delete my_clip.onEnterFrame;
}

btn.onRollOut = function() {
what i need to code here
}
}

if you want it to start again wouldnt you do

Code:

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btn.onRollOut = function() {
        my_clip.onEnterFrame = function() {
          this._x+= -2;
        }
}

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