Hi,
Can do by multiple ways.
create these two Start/End date object in the universe and keep same logic in the objects select part which you have mentioned in the predefined condition.
Drag these objects in the webi query.Whenever report is refreshed on based the predefined condition,you will get the same values in these objects in webi.
If this will not work then what is the logic behind Start date & End date in universe.
Amit