xlsread multiple files from multiple folders

I want to xlsread and xlswrite every .xls file within each folder from a group of folders (58 total folders).

This code works for one file:

f = dir('Y:\Projects\Round\test.xls')
sheet = 'Logic';
[num,str] = xlsread(f,sheet,'D5:D5');
n = 675;
    if str == "Test"
        xlRange = 'D1';
        xlswrite(f,n,sheet,'D7:D7')
    end

This is semi-finished code where I think it would work for one folder, but I want it to loop through every folder within a folder.

files = dir('Y:\Projects\Round\*.xls');
sheet = 'Logic';
nFiles = length(files);
for i = 1:nFiles
    fName = files(i).name
    [num,str] = xlsread(fName,sheet,'D5:D5');
    sttd = 675;
    if str == "Teset"
        xlRange = 'D1';
        xlswrite(fName,sttd,sheet,'D7:D7')
    end
end

Problem with this code is that when I get the name of the file and put it into xlsread, it assumes I am working in my current folder and not somewhere else. instead of fName I need the whole directory.