Make make form dirty if an Iframe is dirty

Hi,

I have a question that I can't seem to find a straight answer too. I tried several things, but nothing seems to work.

In CRM 2016 (on prem) I have a custom Iframe embedded into one of my forms. The Iframe contains several editable fields. Is there any way to set the main form's dirty flag to true, when one of the Iframe's field is edited, effectively making the save icon in the bottom right corner turn blue? 

Thanks!