Look at the case, if you only edit a macro to change a value 123 to 456 and then you save the file, normaly the file size change randomly. So, why ? More, sometimes if you open de file and inmediately you save it, without change any character with another name the size change. May you test it? So, the value of the function is not stable, and you can not determinate if a file was modify or not, using this parameter, because the secuence: open and save change the value. In addition, looking at the properties of the file from the directory, two values appear: size and size on disk that do not correspond to the measurement obtained with the instruction.
It is possible to obtain the size file value with some visualbasic statement that matches the result that appears in the directory Greetings.