Data from where?
D1(end,end,end,64) = 0;
will resize your matrix to this size that you can fill in, but there may be better methods depending where your data will come from, e.g.
D1 = cat( 4, D, otherD );
would concatenate another matrix, otherD, of the same size as D along the 4th dimensions to make it 104*242*64*2
