How to make up an unallocated portion to 100% for a Pie Chart

Hey guys

I need to show time distribution in the form of a pie chart. I am relying on people allocating 40 hours a week of time, however time can be left unallocated. The pie chart can show that 100% of 30 hours was allocated, however this is misleading as it is not 100% allocated in terms of 40 hours.

The records are compiled in a sql view and are made up of many entries making up a week. I can pin it down to a 7 day date range, and assume that it will always be 40 hours. How to i calculate the missing time and show it seamlessly as just another section on the pie chart?

I'm working on an idea of creating a 'command' under database expert, which will be a summarised version of the original view, complete with subqueries to make up the time, creating a (sql) union query of sorts to the view also under database expert. If it allows me to do such a thing.

Also I have a requirement to keep the colours consistent in subsequent pie charts. One chart for each person is shown on the same report. To do this I need to 'create' records with a value of 0% to act as a place holder for that colour. This will make the charts more user friendly as it would be more easy to compare the distribution at a glance.

I believe fixing one will give me the key to fix the other.

Any ideas? Surely someone has had these problem before.