Function IsOutlookInstalled() As Boolean
Dim ret As Object

On Error GoTo OutlErr
Set ret = Application.VBE.ActiveVBProject.References.AddFromGuid _
    ("{00062FFF-0000-0000-C000-000000000046}", 6, 0)
IsOutlookInstalled = True
GoTo ExitProperly

OutlErr:
'No GUID present in Registry
If Err.Number < 32812 Then
    IsOutlookInstalled = False
End If
'The type library is already referenced
If Err.Number = 32813 Then
    IsOutlookInstalled = True
End If
ExitProperly:

On Error GoTo 0
Set ret = Nothing

End Function