I want to create a Chart View using Open Duration as one of the filtering parameters i.e. Number of calls with an open duration in excess of 14 days. Unfortunately the "Open Duration" field doesn't appear in the the "advanced" selection tab.
I think that this is because the Open Duration is a calculated field and not a database field. I think you will need to use a third party reporting tool that can calculate this for you as it opens each record to include in the report.
There are a number of calculated duration fields that are avialable for table views and they are calculated as the record is displayed. For example in a table view you can display diffences in fonts based on remain duration but only when the "field" is on the view as it needs to be calculated. Otherwise you would be putting a large load onto the system to be continually calculating these values.