Setting Granular Calendar Permissions Through Powershell (Without Using Roles)

Hi There!

I have a strange problem... I might even go so far as calling it a bug? I have a request from a client to set a specific set of permissions across all calendars in their business. They effectively want all users to have the "Editor" permission role, with one small change, they want the "Delete" permission switching to Own Items only:

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So, off I go to Set-MailboxFolderPermission to set the permissions manually as so:

(Get-Mailbox) | ForEach-Object {Set-MailboxFolderPermission $_":\Calendar" -User Default -AccessRights ReadItems,CreateItems,EditOwnedItems,DeleteOwnedItems,EditAllItems}

Imagine my surprise when this happens:

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It removes the read permissions entirely... Making the permissions I have just set pretty useless.

If I use:

(Get-Mailbox -identity "mailbox") | ForEach-Object {Set-MailboxFolderPermission $_":\Calendar" -User Default -AccessRights Editor}

It sets the Editor role, which has the Read permissions set correctly, but also sets the Delete permission to All. Unfortunately the cmdlet won't let you mix granular permissions with roles in the same command, and you can't run the commands one after the other as it erases the previous commands settings...

So... what can I do here? Is there a secret command that I'm missing?

Is there a way of doing this in powershell? Thanks in advance!

n5