Personas: How does extra TAB action works?

Hi Personas experts,

In Tab control one can check the "Tab cach enabled" to add extra actions. As did for a Script Button, I add simple script, such as displaying a value in a text box, inside such an extra action of the Tab control.

But no matter I click the Tabs or reload the UI, the action did not happen. Can anyone explain:

1. Did I do the right way to add actions for Tab control? and why doesn't my implementation work?

2. How does Tab action work normally?

Thanks a lot!

Dong Zhu