Detecting on what frame my MC has stopped

[s3ns3]

Hi there,
i was wondering how can you detect on what frame an MC has stopped?
For example i have an MC, and i want to check if it has stopped in the middle of the time line, and then to play the MC, or leave it stopped.

f1 is my button's instance name, and it loads text NR. 1, also, it brings down the background for it. I have other buttons, which i also use to load text, and if the background has not been dropped, it also has to be done, but if it's already there, then i don't need to repeat the dropping animation.

f1.onPress = function() {
if(the frame in txt_bg mc is not the one with background){
    txt_bg.gotoAndPlay(1);}
}