Welcome to the Community, ApexBoss.
I know how important it is to keep track of our budget in the system. However, in QuickBooks Desktop, the option to notify us if we exceed our budget is unavailable.
While this isn't available, I'd recommend submitting your feedback to help improve the program by going to the Send Feedback Online feature in QuickBooks Desktop.

As a workaround, I recommend keeping a close eye on the budget to avoid overspending.
To know more about how the budget works in QuickBooks, check out this article: Create a budget or forecast in QuickBooks Desktop. On the same link, we'll find what report to pull up to review our budgets and forecasts.
Additionally, I recommend customizing the report to get the specific details you need. You can also memorize it to save its current customization settings. It serves as your record and helps you quickly access it for future use.
Please let me know if there is anything else I can do for you, ApexBoss. I'm always willing to assist. Have a wonderful day!