switch from point to comma in float numbers

Hi, i am doing a data logger on my yun, i managed to save data to a file in csv (actually is semicolon separated values).
i noticed that when i import my csv file, excel only accepts to plot (chart?) data if a number has a comma for decimals and not a point (1,3 is ok 1.3 does not plot)
how can i force my sketch to save numbers in xx,xx format?

Thank you.
Fabrizio

I'm quite sure that excel has worked with points for about one day, then suddenly it has stopped making charts with points, yes i think that fixing excel is easier... maybe it's os related, now that i think about it the first tests were done on another mac...

Yeah, just fix excel.

Or you can patch the print.cpp file to use a , instead of .