Schedule a workflow to trigger at a certain time

I want to be able to schedule a workflow to fire at a given time EVERY day based on list membership.

As an example one of our Lead Status steps is "On Prospection" which means we haven't been able to establish contact with the lead via email/phone.

I would like to be able to automatically create tasks and assign them to a specific task queue first thing each morning based on a contact being a member of the list "On Prospection" where:

i) Lead Status = On Prospection
ii) Next Activity Date = Unknown (i.e if there is already a task, we don't duplicate)

If there is already a solution allows me to do this, please point out, but not been able to figure it out. I think the addition of Relative Dates to list filters might help us, as we could combine:

i) Lead Status = On Prospection
ii) Next Activity Date = Unknown
iii) Last Activity Date = "Unknown" or "Yesterday" --> not currently possible

In this case, re-enrollment in the list - and therefore task creation - would happen just past midnight each day