Flash giving me an error for no reason?

1

so i used this code:


onClipEvent (load) {
    adding = false
    subtracting = true
}

onClipEvent (enterFrame) {
    if (_alpha <= 25){
        adding = true
        subtracting = false
    }
    if (_alpha >=65) {
        adding = false
        subtracting = true
    }
    if (adding){_alpha ++}
    if (subtracting){_alpha --}
}

and flash keeps telling me that the “onClipEvent (enterFrame)” function is only available to movie clips. the problem is that what i applied this code to IS a movie clip, what gives?
PS: i converted a button to a movie clip. (from the common libraries)
thanks for the help