Only allow paste to tinyMCE text area under certain conditions

[JoPhi]

Hey guys 'n gals,
with the help of Joomla and tinyMCE I do free German classes on the web. I noticed that users use copy and paste to bring in new articles ( = homework in my case). I want to forbid this under certain conditions/circumstances, primary to avoid that participants steal homework from other participants.

If the text is copied from an area where at least one of the the content's class elements contains "allow-copy-and-paste" I want to allow pasting to the tinyMCE textfield. And if none of the clipboard elements contains such a class, I want to deny the paste-function.

Is something like this anyhow possible?
I'm not that good in Javascript, but I think this'd be the way. I found a way to deny everything (and I think this way–instead of the clipboard content–just paste '' into the textarea).

If yes, could you please give me an advice where I can find information about a conditional paste and/or the necessary steps, or how I can search further?

Thanks so much,
JoPhi