Microsoft is not providing a 64-bit version of VBA for developers; therefore, the 32-bit applications you develop will need to be ported for 64-bit AutoCAD releases. In 64-bit, VBA will run as an out-of-process component, accessed through a 32-bit-to-64-bit ‚Äúthunking‚ÄĚ layer.
The behavior of VBA in the 64-bit version of AutoCAD is not guaranteed to be identical to that of VBA in 32-bit AutoCAD. For example, when the VBA IDE is active or when it is displaying a modal window, there might be a slight delay during the repaint of an AutoCAD window.
For further information, please consult the AutoCAD Migration Guide.