how to populate a crosstab table from dropdown selection ?

I have a dropdown box and a crosstab table which is based on a hierarchy dimension.

In the Dropdown Box(DDB.FRUIT) with Hierachy item(TBL_FRUIIT_HIERARCHY):

----------------------------

Sour Fruit

Sweet Fruit

Bitter Fruit

Crosstab Table

Sour

+Citrus

      -Orange

      -Lemon

My question is how do i pass the value from drop down box to Crosstab table in the on event script.

if (DDB_FRUIT_HIER.getSelectedValue() == "Bitter Fruit") {

  DS_FRUIT.activateHierarchy("ABC1230__ABC1122");

  DS_FRUIT.assignHierarchy("ABC1230__ABC1122", "Bitter Fruit");

TBL_FRUIT_HIERARCHY.getSelectedMember("ABC1230__ABC1122").externalKey);

Not sure i am correct or not..

Regards,

Joseph