This VBScript example checks the size of the item after an embedded attachment has been added and displays a warning if the size exceeds 500,000 bytes.
Sub Item_AttachmentAdd(ByVal NewAttachment)
If NewAttachment.Type = 1 Then
Item.Save
If Item.Size > 500000 Then
MsgBox "Warning: Item size is now " & Item.Size & " bytes."
End If
End If
End Sub