Shared Worksheets between Excel 2007 and 2010.

Hi

We are having issues with Sharing worksheets between Users on Excel 2007 and Excel 2010. Sometimes the file becomes corrupted and can only be opened in excel 2010. Also the File size seems to jump up and almost double in a day.

Is this behaviour expected ? Would it be better if all users sharing worksheets be on the same version of Excel ?

thanks for any responses.

Jason.