Dynamic Filter in universe

Hi ,

I have Two filters (F1 & F2) in my universe , and I have a sechuled report Webi sending by email every Hour from 6AM Day-1 until  6AM Current Day

I want to create a Dynamic filter  that includes the twoo filters , such  if My SYSDATE  'dd/mm/yyyy hh24:mm:ss '  do  not yet passed midnight , Universe use F1 , otherwise universe Use the second filter F2

How can I do ?

Thx