Have a look at MIDP API, interface Choice:
public int getSelectedFlags(boolean[]�selectedArray_return)
Queries the state of a Choice and returns the state
of all elements in the
boolean array selectedArray_return. NOTE: this is a result parameter.
It must be at least as long as the size
of the Choice as returned by size().
If the array is longer, the extra elements are set to false.
so, I suggest you to try (suposing that your ChoiceGroup/List is named list):
Hope it helps,
Horaci Macias