Hi Ganesh,
If you want to do this in HANA modeling and not through reporting tool then we can do this in Sqlscript calculation view.
Below is the sample logic which I'm trying to give you some idea of doing:
BEGIN
-- Declare all the variables used in script
DECLARE REPORTING_LEVEL NVARCHAR(10) DEFAULT '';
IF REPORTING_LEVEL = 'VENDOR' THEN
TAB_RESULT = SELECT VENDOR, YEAR, ....., SUM(FORECAST) AS FORECAST
FROM ......
GROUP BY attributes....
ELSE
TAB_RESULT = SELECT VENDOR, YEAR, ....., 0 AS FORECAST
FROM ......
GROUP BY attributes....
END IF;
Regards
Raj