Agree with kpescatore, as you are using Current Date, then use dynamic dates. Current date - 45 days. Simple. It will make for more efficient SQL too as you will get a "DateField = 'ccyy-mm-dd' clause rather than a subquery.
I would only use the Applysimple here if youyr date table is not matching your current date - i.e. you plan to run after midnight and still call yesterday, today (and today's date is the latest value on the date table).