vba - How to locate data source for unbound control? -

i've inherited access vba code , there controls on form (such listbox named lstorderid, mentioned below) have no rowsource property set (an empty string). in code , find statements in various places:

• forms!frm_customer.lstorderid = rstcust!orderid ' set record set
• forms!frm_customer.lstorderid.requery
• me.lstorderid = me.lstorderid.itemdata(0) ' set first item in self

but in code lstorderid.rowsource being set.

how can requery called on listbox has no rowsource?

how can listbox set single value (rstcust!orderid) record set, unless list of values (although debugger shows integer in lstorderid.value)?

here more code:

dim rstcust recordset set db = currentdb set rstcust = db.openrecordset("select * orders custid=" & id & _                 "and datetaken =date() " & _                 "and vendorid='" & forms!frm_customer.cbovendorid & "'")  forms!frm_customer.lstorderid = rstcust!orderid  rstcust.close db.close 

another section:

dim rstcust recordset dim blstatus boolean dim strsql string set db = currentdb        strsql = "select orders.orderid " & _             "from orders " & _         "where (((orders.datetaken)=#" & date & "#) " & _         "and ((orders.vendorid)='" & forms!frm_customer.cbovendorid & "') " & _         "and ((orders.custid)=" & id & "));"  set rstcust = db.openrecordset(strsql) forms!frm_customer.lstorderid = rstcust!orderid  forms!frm_customer.lstorderid.requery forms!frm_customer.lstorderid = rstcust!orderid  rstcust.close db.close 

also this:

me.lstorderid.requery me.lstorderid = me.lstorderid.itemdata(0)