I've never configured anything like that but i understand now what your trying to do.
There maybe a way in advanced setup (setting it as uncommitted for both lnb1 & 2 and setting the diseqc function up for both lnb's) but it eludes me at the moment.
I'll read up on it and get back to you if i get anywhere.
With a receiver a powerful as yours, i'd consider adding a dual tuner to get the most out of it though.
Thanks for advice. I'll try also...
I fully agree about dual tuner, but unfortunately I have no space to pass 2nd coax-line... maybe (I hope) in the future...