add a collapse expand button

I'm currenly changing from VirtualStringTree to AdvStringGrid I had problems.
I would like to add a collapse expand button at DataArray in the example below  adding the 3 items below it including the columns, which is the best way to go about it.
BTW the values are updated constantly, works good so far.

example layout
Varible          Value    <-Header
MyVar              3
DataArray         55,44,69
DataArray[0]      55
DataArray[1]      44
DataArray[2]      69
MyVar2             3

Did you try calling

grid.AddNode(2,3) (to put the node at the 2nd row, DataArray) ?
 
Yes just figured it out I needed to add a fixed column for the button to make it work with AddNode.
Thanks