Have 2 iCloud calendars with different apple ids

Depending on what you want to achieve you can either subscribe to a calendar or share a calendar.

Subscribe to a read-only copy on your device. See Apple's support document Set up multiple calendars on iPhone

Subscribe to a calendar

1. Go to Settings > Calendar > Accounts > Add Account > Other.
2. Tap Add Subscribed Calendar.
3. Enter the URL of the .ics file to subscribe to and any other required server information.

You can also subscribe to an iCalendar (.ics) calendar by tapping a link to the calendar.

Share write-access to edit events:

Share iCloud calendars on iPhone

In the Calendar app, you can share an iCloud calendar with other iCloud users. When you share a calendar, others can see it, and you can let them add or change events. You can also share a read-only version that anyone can view but not change.

1. Tap Calendars at the bottom of the screen.
2. Tap  next to the iCloud calendar you want to share.
3. Tap Add Person, then enter a name or email address, or tap  to browse your Contacts.
4. Tap Add.

Your boss needs to add a delegate:

Share calendar accounts on Mac - Apple Support