Retaining Connection in flow services

Hi I am developing a webMethods flow service which will be connecting to a database server.
I need to retain my connection handle to facilitate transaction control.

My main flow service need to execute a java flow service which will create the connection and returns the connection handle to the pipeline
I need to pass this connnection handle to other java or flow services from the main flow service.

Also this is used for transaction control where the webMethods Flow service will use the connection object between open transaction and close transaction calls.

Can anybody tell me how I can achive this ?