hi, help needed!

i'm doing a vb.net project!
i use MS Access as my database at the beginning.
so i use:-
CDate(valid_date) < # " & DateTime.Now.ToString("dd/MM/yyyy") & "#
to get some record that the valid_date is < than today date!
it work well when using MS Access.
(NOTE: data type for valid_date is in VARCHAR)

but when my move my database to Oracle.
it has a problem!
i cannot use the CDate function.

so any help can be provided regarding compare the date when database is store in Oracle!


regards;
charlotte