The Basic PayPal e-commerce Widgets don't have this feature. However, you can add PayPal buttons connected to your inventory by customizing your settings on PayPal. Please visit this link for more information: Create a Button That Tracks Inventory Levels.
This will ensure that your product is never oversold, as well as give you an email letting you know when your stock gets low.
Alternatively, consider the Online Store. With a range of management features from order management to stock management, the Online Store is scalable, flexible and powerful.