Powershell and WhatIf

Hi,

I've been asked to look at turning mailbox auditing on on our Exchange Server. Looking around there is plenty of information on Powershell commands to do it. However, I want to look at limiting it to mailboxes within a particular mail database at this point and so I have applied the -WhatIf command to see what the result would be before applying but I get an error. I dont use Powershell a great deal as yet so am unsure as to what I might be doing wrong here:

Command that I was trying to run:

$UserMailboxes = Get-Mailbox -Database 'Database 01' -Filter {(RecipientTypeDetails -eq 'U
serMailbox')} $UserMailboxes | ForEach {Set-Mailbox $_.Identity -AuditEnabled $true} -WhatIf

Error:

ForEach-Object : Cannot bind parameter 'Process'. Cannot convert the "-WhatIf" value of type "System.String" to type "S
ystem.Management.Automation.ScriptBlock".
At line:1 char:126
+ $UserMailboxes = Get-Mailbox -Database 'Staff 06' -Filter {(RecipientTypeDetails -eq 'UserMailbox')} $UserMailboxes |
 ForEach <<<<  {Set-Mailbox $_.Identity -AuditEnabled $true} -WhatIf
    + CategoryInfo          : InvalidArgument: (:) [ForEach-Object], ParameterBindingException
    + FullyQualifiedErrorId : CannotConvertArgumentNoMessage,Microsoft.PowerShell.Commands.ForEachObjectCommand

Am I missing something in the original command or should be structuring this differently?

Thanks.