Input in BADI/cube field in exit?

Hi,

Gone through some of the docs. But still have some query!

I need a calculation of Order date - input date in bex. Order date exists in query.

If I want exit, then input is very easy. But how can I call the order date of cube for every record?

If I go for BADI, then order date in cube can be called...how about input variable?

Which one's better?

Any sample code/docs might help!