working with two listbox

I have two listbox's , listbox 1 and listbox 2 , listbox 1 contain some items e.g :- methane, ethane , propane , I am trying to select these in listbox 2 in different order or sometime just one item , these item have certain properties like Tc , Pc and w which are variable for each item in listbox 1 ,
question:-
when ever i select item or in combination or single into listbox2 , i want listbox2 to read the properties(Tc, Pc ,w) from database , and later i want to use these properties in mathematical calculations but so far i need to know how to read the properties from database based on selection of item from listbox1 into listbox 2
kindly need your help in this
Regards
Qazi