Write a binary string on .csv file in the same location

I have imported a .csv file on matlab and I now have to write on it some data. I need to convert a number on the .csv file from decimal to binary, and then write the binary on a different location on the .csv file, but what happens is that it creates another file with the same title and writes there the number. Moreover it doesn't print on the same location, but starts from that location and then continues on the columns on its right. The code I write is csvwrite('fileName.csv', binaryValue, row, column)