property dragged

This property returns if a box is in the middle of a drag operation. It will be true until the drag operation completes (or is canceled).

var bx = scene.getBoxById("customBox");
var titleBx = scene.getBoxById("custTitleBox");

if (bx && titleBx && bx.dragged)
{
    titleBx.label = "Drag Operation In Progress...";
}