Delete Photos that have been uploaded to Google Photos

I am using the Backup and Sync Google Desktop Uploader to automatically upload photos from a watched folder to Google Photos. But after they are uploaded, I dont need them any more and would like to have hazel delete them, but i dont know a way to make Hazel know if they have been uploaded or not.

Anyone have any ideas?

Check the metadata and see if any of it changes when uploading the file. Perhaps the last opened date gets updated or something else. Alternatively, if the uploader has an option to set a color label/tag after it's done, that could be used.