Setup secretary permissions to manager Calendar in Office 365

Using this article: http://3water.wordpress.com/2013/02/07/office-365-share-calendar-secretary-mode/, I tried to give secretary permissions to manage his manager Calendar:

PS C:\Windows\system32> Set-MailboxFolderPermission -Identity manager@company.com:\calendar -User secretary@company.com -AccessRights Editor

And getting this error:

There is no existing permission entry found for user: secretary.

    + CategoryInfo          : NotSpecified: (:) [Set-MailboxFolderPermission],

    UserNotFoundInPermissionEntryException

    + FullyQualifiedErrorId : [Server=BLUPR05MB152,RequestId=123455ad-db07-481

   3-bdff-dcc7c69007f6,TimeStamp=10/20/2013 7:29:10 AM] CD99E0A2,Microsoft.Ex

  change.Management.StoreTasks.SetMailboxFolderPermission

    + PSComputerName        : pod51042psh.outlook.com

Then, I found this article, explaining difference between Add-MailboxFolderPermission and Set-MailboxFolderPermission:

http://www.nitingupta.in/blogs/index.php/2010/06/21/exchange-2010-sp1-addmodify-mailbox-folder-permissions-add-mailboxfolderpermission-and-set-mailboxfolderpermission/

This directed me to proper way to setup permissions to secretary to manage his manager Outlook Calendar. It is similar to setting permissions from managers Outlook client:

First – make mailbox visible:

Add-MailboxFolderPermission -Identity manager@company.com -User secretary@company.com -AccessRights FolderVisible

Give permissions to Calendar:

Set-MailboxFolderPermission -Identity manager@company.com:\calendar -User secretary@company.com -AccessRights Editor

If you getting error when trying to Add-MailboxFolderPermission:

PS C:\Windows\system32> Add-MailboxFolderPermission -Identity manager@company.com -User secretary@company.com -AccessRights FolderVisible

An existing permission entry was found for user: secretary.

    + CategoryInfo          : NotSpecified: (:) [Add-MailboxFolderPermission],

    UserAlreadyExis…nEntryException

    + FullyQualifiedErrorId : [Server=BLUPR05MB152,RequestId=e9b404d4-0cbb-4f5

   8-9093-6c789ed35297,TimeStamp=10/20/2013 7:56:35 AM] A4EADBBB,Microsoft.Ex

  change.Management.StoreTasks.AddMailboxFolderPermission

    + PSComputerName        : pod51042psh.outlook.com

Then, all permissions must be cleared out:

PS C:\Windows\system32> Remove-MailboxFolderPermission -Identity manager@company.com -User secretary@company.com

PS update:

Now it could be done from web Exchange admin center:

Open your mail box web access, switch to required mail box, click Calender and use small Share link on upper right corner of the page.