Consider only billable hours for time estimate

Hi Community,
I wanted to ask if there is an option to only track billable records against the time estimate of a project?

We have the situation in our projects that only some tasks are billable, some are not. Since we sell billable support hours to our customers, we only want to have the billable hours be tracked against the time estimate in a project. By default, both billable and non-billable hours are calculated against the time estimate.

Thanks a lot for your help!
Florian