Logbook requirements for SARS for claiming travel allowance?

I hadn't submitted my tax forms from 2009 and 2010 (although SARS had owed me money in each of those instances) but I'm trying to resubmit now. I got paid for some of the travel that I conducted from my business (roughly R4/km) and I kep an online logbook on Excel. Is this sufficient for SARS or do I need to fill it out on an official SARS logbook?

If you can convert this to an official SARS logbook that would be better, otherwise ensure that your excel sheet is understandable by a SARS official.