How to find a SCN of a just commited transaction?

 Dear All, I have a scenario like this.

–User logs in to the database
–Executes some DML operations
–Commits his changes
–After this commit I need to find the SCN of this transaction for a different usage. 

I use DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER to get the SCN of my last committed transaction. I am little skeptical that it may not give the SCN of my transaction as there may be something committed in parallel.

Hence somehow I need to find the SCN of my transaction by some way.
Any ideas?
Appreciate your help.
Thanks