How to write a custom average expression within a case or if statement displayed by a dynamic property calculated value

[Jason Elkin]

I've added a calcualted column that sums a time, over three different fields being a property, and two different time categories. The calcualted column looks correct and uses the following expression: time is a real number, and propertyname, timephase1 and timephase2 are strings

Sum([time]) OVER ([propertyname],[timephase1],[timephase2])

I've then created a text area and added a dynamic control calculated value. I want to show the average of the sum([time]) expression above for a particluare value of the timephase2 field. The average function works correctly if I don't use a case or if statement.I've attempted various case or if expressions but I either get no value or that the expression is invalid. Current expression being attempted

case WHEN

[timephase2] ~= "Active" Then

Avg([sum([time]]) OVER ([propertyname]], [timephase1]], [timephase2]])])

END

I was also curious why the double brackets are used after the column/field name, but have also seen similar functions with just the single bracket after the field name. Let me know if any additional information is needed.

Thank you for the help.