Not sure if there is a helper for this or not. Dates can be aquard without helpers.
If nothing else you should be able to do with a script, convert each to timestamp, and the difference will be milliseconds you can divide down to give hours.
Thanks Jesse ive had a look unfortunately the system im using it for is very specific and the default timeclock doesnt work for my setup. Its fine guys ill have a play around and see what i can make happen.