UIButton_OnUpdate_ControlSelected

This callback takes a single parameter. It's only purpose is to enable or disable a button based on whether or not the user has selected a row in a List Box.

The single parameter is:
sListBoxName = The name of the list box we want to check for selection.

If the user has a row selected in the listbox named in the parameter, then the UIButton will be set to Enabled.

If the user does not have a row selected in the listbox named in the parameter, then the UIButton will be disabled.