projectdir = 'appropriate folder name'; %can be '.'
dinfo = dir(fullfile(projectdir, '*_pos_*.sto'));
if isempty(dinfo)
error('no pos file in directory "%s"', projectdir);
end
filename = dinfo(1).name;
Or if you already have a directory structure,
%assuming dinfo is an existing directory structure
filenames = {dinfo.name};
filename = filenames{contains(filenames, '_pos_')};
if isempty(filename)
error('no pos file here');
end
