Have a look here: DB-specific Relative Dates SQL Server, Oracle, Netezza, DB2
Halfway down the page, I posted several bits of code for dates that work in multi-source IDT. Took me ages to figure out but IDT has its own peculiar syntax so that code works with different databases.
May not help, but might point you in the right direction!
debbie
Debbie 
(BOB member since 2005-03-01)