OK, due to almost overwhelming demand, I have put my modified version of the spreadsheet online.
Right-click
here and choose "Save target as" for the compressed version (120k), or
here for the uncompressed version (500k)
This one will work out the times for you given flight start and finish times in HH:MM format and will put them in the SEP or MEP columns as appropriate as long as you have set up the aircraft types at the top of the sheet.
It will also sort out the day and night entries if you choose 'D' or 'N' in column 'J' - it defaults to day if you leave this blank. If a single flight includes both day and night time then you'll just have to work out the split yourself and enter the numbers into the right columns manually.
To look up the airfield names and codes, click in the cell where you want the name to end up then press the three keys 'Ctrl, 'Shift' and 'A' at the same time. Highlight the airfield you want and press OK.
The list has most UK, French and New Zealand fields with ICAO designators. You should be able to work out how to add more of your own. If not, I will consider requests written on on the back a £10 note
I use it as a backup to my paper logbook and find it very useful. Your mileage may vary.