but if you've got a linux machine anywhere nearby you could use GnoTime.

" GnoTime Tracking Tool
utility for tracking and invoicing time spent on projects
GnoTime is the GNOME Time Tracker, a program which allows you to track the time you spend on any number of tasks and projects. GnoTime also allows you to generate customised reports and annotated logs of these times.
Tasks within GnoTime can be marked as billable, non-billable, on hold, or free of charge, and invoices can be generated based on these data.
GnoTime also includes various features such as sub-projects, project planning, scheme extensions and automatic merging and clean-up of short intervals of time.
Version: 2.2.2-6 (gnotime)
GnoTime Tracking Tool integrates well into the Ubuntu desktop"

sounds like it does exactly what you're looking for, for free.