Track elements of preview file/DOM of prreview files

I have created an application,in which I am embedding box platform.After uploading a fileto box,i will get an embed link to preview that file.

Through that embed link i can display uploaded files in my website.My question is that,if suppose i uploaded PPT file containing 5 slides.After previewing that file in my application,I want to evaluate time spent on each slide.

But as my application domain & box domain is different,I am not able to get DOM(DOCUMENT OBJECT MODEL) of   page which  I got from Box Platform.

Another solution I used is make an ajax call to my web service,after getting html page from box,I reverted it to browser.But it executing js & css files,but not making api call to fetch the attribute regarding that files.

Please help me.....

Thanks in advance.