On Error Resume Next

' Try to get running instance of Outlook
Set outApp = GetObject(, "Outlook.Application")

If Err.Number=429 Then
    Err.Clear
    MsgBox "Outlook isn't running so I'll try and start it"
    Set outApp = CreateObject("Outlook.Application")
    ' Check to see if Outlook started or not
    If outApp Is Nothing Then
        MsgBox "Outlook didn't start, sorry!"
    Else
        MsgBox "Looks like Outlook was started okay!"
    End If
Else
    MsgBox "Outlook is already running, so I won't do anything"
End If