I'm another who uses paper and logbook.aero. I was using a spreadsheet and the guy at logbook.aero imported it for me into his website. You can export back out again, so every now and again I'll do an export so that if the site has a problem I wont lose it all.
Time is awkward in excel but my old one did it ok.
I put date, start and end times as different columns, with the time custom formatted to hh:mm.
Then doing Maths on it seemed to work (so total airborne time = end - start, etc.) so long as you keep setting the formatting.
Slightly annoying when doing totals which is maybe what you're doing G? in that once you get to 24 hours it makes it up into a day, rather than saying you have flown 24 hours. To change it back to hours you need to multiply by 24 (which will give you hours in decimal), then you need further manipulation to convert the decimals into minutes.