The RXSUBCOM command registers, drops, and queries Rexx subcommand handlers. A Rexx procedure or script file can use RXSUBCOM to register dynamic-link library subcommand handlers. Once the subcommand handler is registered, a Rexx program can send commands to the subcommand handler with the Rexx ADDRESS instruction. For example, Rexx Dialog Manager programs use RXSUBCOM to register the ISPCIR subcommand handler.

"RXSUBCOM REGISTER ISPCIR ISPCIR ISPCIR"
Address ispcir

See Section 2.1, “ADDRESS” for details of the ADDRESS instruction.