How so I separate the front two channels of a 4 ch recording, to decode mid-side?

I am recording in 4 channels into a Sound Devices 744T. Front pair is in mid-side config, rear pair is two Omni mics. When I open these files in AA3 they show up as 4 mono channels. How do I separate the first two channels to decode the mid-side using Voxengo plug-in.