I had similar problems passing parameters to Outlook.
On some windows machines, this @Formula worked perfectly:
@Command([Execute]; "Outlook.exe"; "/recycle")
On Windows Terminal Servers, it caused Outlook to be unable to parse the "/recycle"
The Shell-command from LotusScript wasn't even able to locate the Outlook.exe, as it was not in the PATH.
Ralf's code helped me in this respect. The "WScript.Shell" seems able to interact with Windows registry settings. Anyway, here is the code that works for activating an open Outlook window.
Dim objShell, returnValue
Set objShell = CreateObject("WScript.Shell")
returnValue = objShell.Run("outlook.exe /recycle", 3, False)