The IntelliGantt Web Part for Basecamp lets you keep additional fields associated with specific Todo Items. Two such fields are Hours and Cost. Because they are numbers, the IntelliGantt Web Part for Basecamp will do basic rollup calculations. Both of these fields can contain decimal numbers.
Below is the initial view you may see for a Basecamp project.
If you scroll the task grid all the way to the right, you will see these two additional fields: Hours and Cost. They will not be available in the Basecamp UI, but their data is stored in Basecamp so every other user of the IntelliGantt Web Part for Basecamp will see the same data values.
Here we enter a few Hour values. Notice that the Todo List container the Todo Items rolls up the hours. Likewise, notice that the top level project rolls up the hours as well. This gives you a high level view of the hours in your project.
Similarly, the IntelliGantt Web Part will work the same for the Cost field.