Hi Abhijeet
When you change the PO, what events do we see in SWEL? (provided it is switched on using SWELS). You can use those events to start the WF, however, you need to build in artificial Intelligence to check that the workflow starts only for your condition.
I am assuming that when the Value increases, the release strategy is RESET (based on functional config)....which triggers event RELEASESTEPCREATED - the starting event of your workflow as on date.
Now, for your new case, obviously, the release strategy is not reset.... and RELEASESTEPCREATED is not triggered.
One option is to check with the Functional Owner to see if they can configure to reset the release strategy for this new case...then there is no development change required because RELEASESTEPCREATED would trigger the workflow.
However, if that is not possible via config - check for the event triggered - most probably, it would be BUS2012.CHANGED.....set this event as a start event (additional to RELEASTEPCREATED). But remember, this event triggers for any change. So, create a check function module (or best, a first step in the workflow) to read what was changed and check for your net value change - if changed, then let the execution go normally to continue the WF else end it using a process control step.
Regards,
Modak