DS

If you have Matlab(2006a) or newer, you can use the 'split' option of the builtin function REGEXP to split a string into a cell array of substrings, like so:
parts = regexp(myText,’\s+’,'split’);

"x{i} = 1:5" is faster than "x(i) = {1:5}".
It would look nicer and save some micro-seconds to compute "floor(size(C,DIM)/nout)" once only and store it in a variable.
"ndims(C)" is nicer than "numel(size(C))".
The VARARGIN in the inputs is not used, so I suggest to omit it.
The first element does not need an exceptional handling, therefore I'd include it in the loops to simplify the code:
q = floor(size(C,DIM)/nout);
for i = 1:nout
x{i} = C(i*q - q + 1:i*q, :);
end
A method for indexing along any dimension:
Index = cell(1, ndims(C));
Index(:) = {':'};
for i = 1:nout
Index{DIM} = i*q - q + 1:i*q;
x{i} = C(Index{:});
end
But this is slower than the explicite method.

A very well documented and nicely written function. Useful and usable, vectorized and check of inputs.
A suggestion: The check of the size of R crashs, if R has more than 2 dimensions: "if (size(R)==[1 1])". "if numel(R)==1" is saver and faster. Afterwards rejecting "numel(R)~=2" is sufficient and accepts a [2x1] column vector also.