@dane60 Thanks for the question.  Where is the billable amount you are referring to that you don’t want to exceed?  Could you please be more specific on what you are attempting?

If you are using Pro Forma invoices, you can use the “Use T&M Revenue Budget Limits” checkbox that is available on the Summary screen of the project profile:
From Acumatica’s documentation here: https://help.acumatica.com/Help?ScreenId=ShowWiki&pageid=c17cd276-1245-4e6e-a687-fa3ccdaa1e16 

• On the Revenue Budget tab of the Projects (PM301000) form, you can define billing limit amounts for revenue budget lines of the project if the Use T&M Revenue Budget Limits check box is selected on the Summary tab of the same form. The system applies these limit amounts to the pro forma invoices of the project. During entry of a pro forma invoice on the Pro Forma Invoices (PM307000) form, if the invoice exceeds a limit, you receive a warning or an error message, depending on the Validate T&M Revenue Budget Limits setting on the Projects Preferences (PM101000) form.
   

Perfect thank you for you help.