How to Enable/Disable buttons in a tool bar...

CASE STUDY:
I have created a tool bar with four buttons: "New", "Edit", "Delete", and "Refresh". Now, when I press the "New" button, I want the "Edit" and the "Delete" buttons to be DISABLED.
Then, after I press the "Refresh" button, I want every thing to be ENABLED. In other words, to return back as we where when we first opened the application.

The solution will be available soon...