Set notes field from snippet?

I want to extract some data from my sites and fill in the notes field with that value. I essentially want to look up the next schedule of a cron event my sites run (for backups) and update the notes of the site in mainwp so I can use the mainwp api to pull the next backup time for reporting. I am able to look it up in a snippet. is there a way to write that data back to the site’s note field?