Attach at least two files that illustrate the issue -- they don't have to be more than a few lines each.
But, in general, you should be able to write a generic import object; I'd think about all you should need would be
nHdrL=304;
opts=detectImportOptions('AnExampleFile.prc','FileType','delimitedtext','Delimiter','\t' ...
'NumHeaderLines',nHdrL,'Range',[nHdrL+1,1],'ReadVariableNames',1);
The above should give you a good import options object from which to start with some customization to generalize for purpose...
VNAMES={'Date','X', ...,'Fred'}; % the list of desired variables
opts.SelectedVariableNames=VNAMES; % tell it which ones you want
opts.VariableTypes=repmat({'double'},1,numel(VNAMES)); % and the data type
The key is since you don't know what is in the file as to the total number of variables, then telling it a specific number to read will be lying for any file without that specific number. The above will try to find the variables you've listed.
You may need to futz with the 'VariableNamesLine' parameter if it isn't the one line before the data; the default location may not match what you wish; this will particularly be true if there is some other text in the file or somesuch.
Then, save this import object as a .mat file with a nice name and read it into memory and use it inside the loop over the files...
