Canvas HTML DOM getElementById() of specific movieclip

Hey guys, I'm using Animate 2020 publishing export into HTML5 canvas for Google banners. One of the requirements of the platform is to stop all animation after clickthrough. In order to do so, I would like to do the following. 

After publishing *.fla file, inside resulting HTML document I would like to use getElementById() function to access certain movie clip called "mcHolder" at making it gotoAndStop() to a specific frame called "last_frame". So I'm trying to access it this way. This is how exportroot is defined by the publishing process

exportRoot = new lib._20Q2_BANNER_300x250_NL();

Any suggestions on how to make it work? This one below can not do the job.

exportRoot.mcHolder.children[0].gotoAndStop('last_frame');

I understand that this question is more coding related than animation. But maybe someone already figured it out.

kind regards, Tania