Melodic Media

Hello, sorry for the late reply. Just to clarify when you rollover or click on the banner you’d like to show a larger banner say 300 X 600 pixels, inside of this banner you’d like to display an HTML File or URL. You can do this however there is a Cross-Domain issue. (This issue is only for the external URL option) If you copy and paste the HTML it will work fine.
You must place the HTML file URL on the same website that you are using.
For example, If you install the Expandable Banners Plugin on https://www.xyz.com you must load the HTML onto https://www.xyz.com/yourhtmlfile.html

You can always E-mail me at – [email protected] for more support.

I hope that helps answer your question.

Sorry for the late reply, yes this will work with DFP.
You must submit your banner as an HTML Banner.
You will also need to create a new Ad Unit that is the size of the larger expanded banner for example 728 X 500.

Then in Generate Tags section of DFP when you place the code on your site you modify the CSS to be 728 X 90. I hope that helps answer your question.