Open Opportunities with no Open Tasks

Trying to design a report (and dashlet) that tells us which Open Opportunities do not have an Open Task. To keep it simple - Opportunity Sales Stage is not Completed and there is no Task that has a Status that is not Completed.

Its easy to get a report of all Open Opportunities that have no tasks or have overdue tasks - the emphasis with this problem is there could be numerous task that lets say are completed against hte opportunity.

We are looking for Open Opportunities that do not have an Open Task with a due date of today forwards (we have overdue covered).

I looked at the next # days option but that didn't seem to provide a solution.

Any help ideas appreciated.

Sugar Cloud - so code changes are not an option.