Well I guess there is not a direct way. Displaying the comboBox is not the problem, the problem is triggering the event when the choice is selected. I guess you can create a method to get the Selected object and a method to display the popup. Then create a Thread to read the option each 1 second and display the opopu is the option changed.
Now what is ur actual query here ?
Are u asking how to know add a ToolTip kinda thing here ? If thats the case then I don't know the existence of any such kind of thing in J2ME. Why don't u do it in Canvas or make such a high level ChoiceGroup urself by implementing Choice if possible or rather use a CustomItem.
Regds,
SD