Oracle fusion hcm how to validate previous month with current month

Summary:

We have requirement where we want to validate the overtime applied date should be between start date and end date of previous based on current month.

i want to create a value set to pull the value so that i can use in fast formula but not able to create values set with below condition

select
to_char(CASE WHEN TO_CHAR(to_date(:{PARAMETER.P_EFFECTIVE_DATE}),'MM') = to_char(sysdate ,'MM')-1 THEN 1 ELSE NULL END)
from dual

also tried to do from fast formula but the date parameter is not getting validate

DEFAULT FOR entry_value is '0001/01/01 00:00:00' (date)