Forum OpenACS Development: creating multirow inside db_multirow

i want to append a new multirow col inside my db_multirow... and this is my failed attempt

db_multirow -extend {next_states} items item_query_by_resource { }  {
    template::multirow create next_states state

    foreach .... {
        template::multirow append next_states $state
    }
}

inside my adp page
<multiple name="items">
    ....
  <multiple name="items.next_states">
  </multiple>
</multiple>

Error Message
can't read "items.next_states:rowcount": no such variable
    while executing
"for { set __d14_i 1 } { $__d14_i <= ${items.next_states:rowcount}  } { incr __d14_i } {
    upvar 0 items.next_states:$__d14_i items.next_states

}"
....
....

any suggestions??