How to estimate index creation time required?

Hi,

I have to create 2 indexes on ORABPEL schema's INVOKE_MESSAGE and DML_MESSAGE tables(1 each)

I tried to create 1 on INVOKE_MESSAGE yesterday w/o taking application outage,but got stuck due to lock acquired on INVOKE_MESSAGE  by another session.

Now my requirement is to estimate  time required to create the index ?

Is there any way that I can calculate it?

I am planning to use below script:

create index HEADERS_REF_IK on ORABPEL.INVOKE_MESSAGE(HEADERS_REF_ID)  TABLESPACE ORABPEL  PARALLEL 16  NOLOGGING;

--After index creation

alter index  HEADERS_REF_IK parallel 1;

NAME                                 TYPE        VALUE

parallel_max_servers       integer     320