PB如何获取列表框中同时选中的多个项目

integer li_index
integer li_start
String ls_items

li_start = lb_1.SelectedIndex()
if li_start < 1 then return

For li_index = li_start to UpperBound(lb_1.item[])
if lb_1.State(li_index) = 1 then
ls_items = ls_items + ',' + lb_1.Item[li_index]
end if
next

MessageBox('',Right(ls_items,len(ls_items) - 1))