You probably should not be in this situation to begin with. Whatever code you're using to create the cell array, should probably be organizing the data as a 7x2xP numeric array instead. Most operations on an MxNxP array will be more efficient than with the MxN slices split across P cells.
An exception to this is when M*N is large and you're trying to avoid the copies that MATLAB makes when you do things like
a=A(:,:,i)
but the slices would have to be very very large to warrant that.
