Naming variables like Col1, Col2, ... is a very bad coding practice: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval. It is much easier to use cell arrays. For example
Vdata = rand(100, 768);
Col = mat2cell(Vdata, size(Vdata, 1), 64*ones(size(Vdata, 2)/64, 1));
Col is a cell array with each element having 64 columns.