Error adding disk to backup set

Hi

SBS 2011 standard.

I am using option 3 from here https://support.microsoft.com/en-gb/help/2009365/error-message-when-you-try-to-add-an-additional-disk-to-a-scheduled-ba to add a disk to the backup set but I am getting an 'Incorrect function' error. Log below.

How can I add the disk to the backup set if not all disks are connected at the same time?

Thanks

Regards

C:\Windows\system32>wbadmin get disks
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.

Disk name: TOSHIBA STOR.E PARTNER USB Device
Disk number: 2
Disk identifier: {9ca06517-0000-0000-0000-000000000000}
Total space: 931.51 GB
Used space : 931.49 GB
Volumes: <not mounted>[ACMES 2020_08_26 20:25 Disk_02]


C:\Windows\system32>WBADMIN ENABLE BACKUP -addtarget:{9ca06517-0000-0000-0000-000000000000}
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2004 Microsoft Corp.

The scheduled backup settings:

Bare metal recovery : Included
System state backup: Included
Volumes in backup: <Edited out>
Files excluded: None
Advanced settings: VSS Backup Option (FULL)
Location to store backup: ACMES 2014_12_11 10:21 DISK_03,TOSHIBA STOR.E PARTNER USB Device
Times of day to run backup: 23:00

Do you want to enable scheduled backups with the above settings?
[Y] Yes [N] No y

Do you want to format and use TOSHIBA STOR.E PARTNER USB Device (that includes volumes <not mounted>)
as the location to store scheduled backups?
[Y] Yes [N] No y

Label the backup disk as ACMES 2020_08_27 13:32 Disk_02.
This information will be used to identify this backup disk during a recovery.
Incorrect function.