Timesheet, budget, estimate and invoice

Timesheet, budget, estimate and invoice

Selected clients receive a not-to-exceed budget for each project.
First, a timesheet project is set up for each client project.
Then, within the timesheet project setup I add the budget in the budget field.
Finally, I prepare an estimate from within the timesheet project, but I can't figure out how to make the budget the not-to-exceed amount in the estimate. Is this possible?
Finally, will/can Zoho invoice notify me when timesheet project time exceeds the estimated budget? [so I can send a change order for more time]