Sending Event ID in HTTP request body

Hello, we are trying to send a RingCentral event payload (voicemail) to an Azure Function but want to be able to query RingCentral later on when the voicemail recording becomes available. In the request body section, we can insert variables directly like the Caller Number and the time that the call was placed. However, we cannot automatically insert the event ID or voicemail ID into the request body. Is there a way we can reference the event ID in the request body?

Thanks!

-Dan