Sub SendInvoice()
Dim oOutlookApp As Object
Dim oItem As Object
Dim olInsp As Object
Dim wdDoc As Object
Dim oRng As Object

    On Error Resume Next
    'Get Outlook if it's running
    Set oOutlookApp = GetObject(, "Outlook.Application")

    'Outlook wasn't running, start it from code
    If Err <> 0 Then
        Set oOutlookApp = CreateObject("Outlook.Application")
    End If

    'Create a new mailitem
    Set oItem = oOutlookApp.CreateItem(0)
    With oItem
        .BodyFormat = 2
        Set olInsp = .GetInspector
        Set wdDoc = olInsp.WordEditor
        Set oRng = wdDoc.Range
        oRng.collapse 1
        oRng.Text = "This is the message body"
        .To = "someone@somewhere.com"
        .Subject = "This is the subject"
        .Attachments.Add "C:\Path\Invoice No.001.pdf"
        .Display
    End With

    'Clean up
    Set oItem = Nothing
    Set oOutlookApp = Nothing
    Set olInsp = Nothing
    Set wdDoc = Nothing
lbl_Exit:
    Exit Sub
End Sub