Unset Default Signature - PowerShell

Hello, 

I'm looking for a way to unset a default signature and to put it not by default with PowerShell script.

This script show us how set the default mod for signatures but not the opposite.

#Set company signature as default for New messages $MSWord = New-Object -com word.application $EmailOptions = $MSWord.EmailOptions $EmailSignature = $EmailOptions.EmailSignature $EmailSignatureEntries = $EmailSignature.EmailSignatureEntries $EmailSignature.NewMessageSignature=$CompanyName $MSWord.Quit() 

Any Idea ?

Regards, Scanta