Discoverer - Date query and s74 value

hiya,  i'm trying to create a new due to complete report and due to start reports, similar to the one on EXOR reports but with  few additional details, for example whether the job is a permit or NRSWA, and i can't seem to work out how to add the S74 value per day or how to add the countdown (or validity left for due to start)  I think i need a system date to maybe use some calculation?

any help would be appreciated.   thanks Ali