TypeError: Error #1010, while accessing a movieclip from another movieclip as3?

programming flash
1

[LEFT][COLOR=#000000][FONT=Arial]I have got two movieclips on the main timeline. First one is envelope_mc and second is bg_main. In envelope_mc timeline there is a button on 25th frame which plays ahead when clicked. Here’s the code for first movieclip:[/FONT][/COLOR][/LEFT]


on_btn.addEventListener([COLOR=#2B91AF]MouseEvent[/COLOR].CLICK, playAhead);

[COLOR=#00008B]function[/COLOR] playAhead([COLOR=#00008B]event[/COLOR]:[COLOR=#2B91AF]MouseEvent[/COLOR]):[COLOR=#00008B]void[/COLOR]
{
    play();
}

[LEFT][COLOR=#000000][FONT=Arial]I have also got some animation on bg_main which I wan’t to trigger on 30th frame (inside bg_main timeline) when button is clicked in envelope_mc timeline. Here’s the code for second movieclip:[/FONT][/COLOR][/LEFT]


[COLOR=#2B91AF]MovieClip[/COLOR](root).on_btn.addEventListener([COLOR=#2B91AF]MouseEvent[/COLOR].CLICK, playAhead);

[COLOR=#00008B]function[/COLOR] playAhead([COLOR=#00008B]event[/COLOR]:[COLOR=#2B91AF]MouseEvent[/COLOR]):[COLOR=#00008B]void[/COLOR]
{
    play();
}

Complete error:
TypeError: Error #1010: A term is undefined and has no properties.
at Flashphotographygallerywebsite7_fla::bg_1/frame25()