About exchanging data with PowerBuilder – PB Docs 2021

You can use the IPB_Session interface or the IPB_Value and
IPB_Arguments interfaces to exchange data between PowerBuilder and PBNI.
The IPB_Session interface contains many virtual functions that enable the
C++ code in an extension to interact with the PBVM. The IPB_Value and
IPB_Arguments interfaces contain methods that you can use to pass values
between PowerBuilder and extensions.