What Tomas Buryanek has said is correct,
One twick you may try. Inside your CALL FUNCTION.... IN UPDATE TASK.
Try to CALL another FM in BACKGROUND TASK, inside that you can SUBMIT your program.
Or else.. What Praveer Kumar Sen has said can be a good alternative.
You can go for a standard task where you use BUS2032.CREATED/ BUS2032.CHANGED as triggering event and write your code in the Method. you get lots of help over the internet about how to use macros inside a workflow method
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