Task API or something similar to find running BPM/SOA process instances

Hi everyone.

We have a requirement where Process A need to have a check for whether any instances are already running for this process on the same customer. So if Instance A1 is started, and are in any state (In a Human task, not in a human task, in a timer, in recovery...), then when instance A2 is started if check running instances and finds instance A1, and then A2 will terminate right away. This is simplified requirement and not exactly how we need to solution, but for the example this is how we want it.

We have looked into the Task API (