You'll need to get the index of currently selected item in your ListView. Because ListViewControls support multi-selections (although you have to specify it in your XML to actually use this), you have to loop through all rows and see if that row is selected or not. If it is selected, you can use that index.
code:
//Loop from the first (index 0) to the last (index Count-1, Count is not included with the < operator) row in the list
for(var Index=0; Index < PlusWnd.LstView_GetCount("ListView"); Index++) {
//If this item is selected...
if(PlusWnd.LstView_GetSelectedState("ListView", Index) === true) {
//Break out of the loop
break;
}
}
//Do something with Index, like
Debug.Trace("Selected item: "+PlusWnd.LstView_GetItemText("ListView", Index, 1));