I need to have a toggle - when not selected will display all the data in a straight table, however when selected to exclude the top 15% and bottom 15% of the calculated expressions in the straight table ... please assist and guide me in the right direction.
You could try to get an acceptable view of your data with using the restriction tab of the straight table. This meant displaying the area between top and flop would be not possible but many other views are possible especially if variables will be used for the restiction values/borders.
If this isn't enough you will need to use calculated dimension like this one: