What it sounds like to me is that when your closed date field is populated, you want the status to automatically change to 'Closed', and then your items would automatically be grouped into the correct Open/Closed group based upon the status.
I would build a quick workflow in SPD for this to run on an item change. If you haven't already, set the default value of Status to 'Open'. Then, using the workflow, change the Status to 'Closed' when the 'Closed Date' field is not blank.
In your view, group by the 'Status' field, and make sure your Status field is hidden (unchecked) within the view.
This way, you'll have an 'Open' and 'Closed' group, and when the closed date is populated, the item will automatically move from the 'Open' to 'Closed' group.