hi ROHIT....
before invoking other rexx program u should make sure that ...u r called program is presnt in the library which was concatenated to SYSPROC or SYSEXEC library.....( i am assuming here u r calling program is allready concatenated to this DD'S ......if so u can put this called program also in the same library).....
syntax:
ADDRESS TSO "%LIMITTSO " ; ( LIMITSO IS ANOTHER REXX PROGRAM)...