Calling Powershell Exchange cmdlet in VS2010

Hello

I am trying to run a Powershell script in VS2010 on a 64bit 2008 R2 server with Exchange 2007 Tools installed; and failing miserably

The code is:

vb.net Code:

Dim res As String
    Dim runspace As Runspace = RunspaceFactory.CreateRunspace()
    runspace.Open()
    Using pipeline As Pipeline = runspace.CreatePipeline()
    Dim myScript As String
    myScript = vbCr & vbLf & "set-executionpolicy -scope CurrentUser -executionPolicy RemoteSigned -force" & vbCr & vbLf & _
    "add-pssnapin Microsoft.Exchange.Management.PowerShell.Admin" & vbCr & vbLf & _
    "Get-Mailbox -DomainController Myserver.mydomain.com stest1"
    Dim command As New Command(myScript, True)
 
    pipeline.Commands.Add(command)
 
    Dim results As Collection(Of PSObject) = pipeline.Invoke()
 
    Dim i
    For Each i In results
    res = res & vbCrLf & i
    Next
 
    End Using
    cmdOutputTextBox.Text = res

It fails at "PipeLine.Invoke" with:
The term 'Get-Mailbox' is not recognized as the name of a cmdlet, function, script file, or operable program.

The code works everywhere except where it's needed :(

I've tried a few permutations and getting nowhere, can anyone help?

Thanks

Stuart