Another simple way to send the content of an excel compatible file through serial port is by saving the file with CSV formatting, which is nothing more a text format separated by ';' delimiters, but in order to make the communication to be a bit robust you must add in the first and last line extra characters meaning start and end of transmission. It would also be prudent to add optionally on the penultimate line an extra field containing the checksum of the previous lines, something extremely easy to do with the Excel's builtin math functions.