Assume that the content of each items in your listview come from the result of querying of taffydb.
1. Then you could get value of a key by "Expression:Index2QueriedRowContent( index , key )" , index is the "selected" in your case.
2. To save the modified item, uses "Action:Set row index" to set the row id by index. See the section "Insert a row" in my document for more detail.