How to create and expandable crossTab column in Report Studio 8.4?

1- We have this crossTab report that is working just fine

2- It has 3 lines and 3 columns

3- I would like to display only the FIRST line (which is in fact a TOTAL)

4- Then, if the user needs to see the 2 other lines he would simply need to expand a plus sign and then we would see the subTotals lines.

What is the name of this behaviour ? Are we talking about “Expandable columns” and if so what do i need to do ? Or are we dealing with Drill Down functionality ?