Blackboard key value change

Is it possible to change a boolean type Blackboard Key using an on clicked event?

The screenshot that is posted are the nodes that I created for the widget button. As far as I know, based on the nodes I created, Once clicked, The blackboard value should be changed to true. I know I did something wrong or I referenced the wrong nodes. I am just not sure which is which. Please help, this is for a school project. Thank you in advance

Is there any update on this? I think I have a similar issue. My casting is failing all the time and I cannot make it work…