Way to calculate duration for a given time period?
 

I love the way that OmniFocus lets you set estimated duration of a task. What would be really helpful, though, is if there were a way to calculate those durations for things that are due on a certain day or within a certain time frame. Say, for example, I have a passel of tasks due today. It would be great if OmniFocus calculated the time estimates so I could have a sense of whether it is even realistic to think I can do all of those things today.