Please help with hasCheckbox property to ungrey and enable dynamically

In my json declaration for these checkbox tree nodes I declared by default as "hasCheckbox" : false.  How do I programmatically based on met condition to enable the checkbox so that it's not greyed out.  I tried the below code but did NOT work:

Mif.id(nodeId).hasCheckbox = true; // didn't do anything, i.e. this did NOT redraw the node and still greyed out

then I tried the below and did NOT work or enabled, i.e. still greyed out:

var node = Mif.id("AFI");
node['hasCheckbox'] = true;
Mif.Tree.Draw.update(node);

Thank you.