It seems likely that the non-teaching staff here are all going to have to keep timesheets to account for their activities...
I had to do this in 15 minute slots when working "in industry" as my time was cross-charged and didn't have a problem with it.
I just can't see it working here... In my case I'm part-time (at home now - so no time wasting issues!) and my contract covers more than one job... not just the IT. Then there's the stuff that I'm trying to get added in to my contract (actually this might help).
Do other schools have timesheets? Does it work for you as well as the Bursar?