how to use 1st derived tables object into 2nd derived table in Universe

Hi All,

I have 2 derived tables need to use objects from 1 derived table objects into 2nd derived table

1st derived table name India12

object name P1_Start, P1_ End

2nd derived table name India20

sql:

SELECT 'Q1'  as PRD,SUM(MBR_CNT)

FROM

(

SELECT

COUNT(DISTINCT MEH.MBR_KEY)      AS MBR_CNT

FROM MBR M

INNER JOIN MBR_PROD_ENRLMNT_HIST_WGS MEH

ON M.MBR_KEY = MEH.MBR_KEY

WHERE  MEH.MBR_PROD_ENRLMNT_EFCTV_DT <= P1_Start

AND MEH.MBR_PROD_ENRLMNT_TRMNTN_DT > P1_End

the bold objects are belongs to derived table 1

how to use this i am unable to use this

i am using SAP BO universe 3.1

Thanks in Advance..

Ranjeet