@nickoertel
What exactly is your aim? What are you trying to achieve?
So if you can’t send data to an opened Lightbox, so why not closing it and open it again with new refreshed data? (denk ans ausblenden & einblenden). 
Here a simple example, of how to send data to Lightbox…
https://russian-dima.wixsite.com/meinewebsite/lightbox