I really don't understand your question now. You want to have half of the miles (e.g. outgoing) credited to M&B and the other half (return) on M&M? Or do you want the miles (all of them) to be credited to M&B and then, after attaining status, to "move" them to M&M? And, all of that, flying a third airline? The status shown on your boarding card is ALWAYS the status you have with the programme you are crediting the miles to. There is NO WAY that you can satisfy both of your needs, i.e. credit the miles to one programme and using the status of another. As a matter of fact, INDEPENDENt of whether you fly one of the two airlines involved or a third one!