You can use Teamup notifications to have a report sent of all calendar activity each day. This report will include the name of the user or link used to make the changes.
Here's how you would set this up:
Open the calendar in a browser.
From the blue menu icon in the top right, select Preferences > Change Notifications.
Set the options for the notifications to include the sub-calendars you want to include. More details here.
Note that in order to set up notifications, you'll need to be logged into your Teamup user account. If you don't have a user account yet, register for one. It's free.
Have the notifications sent as a daily digest. Each day, you'll receive an email with the change notifications in a list.
Here's an example notification. Note the Modified by: line, which shows the name of the user (or link) who made the change.
notifications, change log, digest, calendar changes, user history, edit history, event history