xlsread csv file commas instead of point

I am importing one column of data with decimals to excel with xlsread. I want this to become a .xlsx file however I have a macbook so I do not know if this is possible. I get this error:Warning: Could not start Excel server for export. XLSWRITE will attempt to write file in CSV format. > In xlswrite (line 181) In eindopdracht (line 14)

I can open the csv file but the values with decimals are separated with a point instead of a comma. I do not want to change the settings of my excel so I was wondering whether there is a script to change all the points to commas in the csv file?