run {execute script duplicateDb(until_sequence => 12345);}

create script DUPLICATE_DATABASE
 {
  allocate channel ch1 type disk format '$ba_ORABACKUP/%U.bck';
  allocate channel ch2 type disk format '$ba_ORABACKUP/%U.bck';
  allocate channel ch3 type disk format '$ba_ORABACKUP/%U.bck';
  set limit channel ch1 kbytes 2024800;
  set limit channel ch2 kbytes 2024800;
  set limit channel ch3 kbytes 2024800;
=======================HERE you can use======================
.
.
.

run {execute script DUPLICATE_DATABASE}