function getCrtlPrefix()
{
       var prefix;             
       var    objCrtlPrefix = document.getElementById("ctrlPrefix");
             

       if (objCrtlPrefix)

             prefix = objCrtlPrefix.value;                 

       return prefix;
}
function readValue(ctrlName)
{

       var prefix = getCrtlPrefix();    
       var    objCrtl = document.getElementById(prefix + ctrlName);
       

       if (objCrtl)
             alert ( "Prefix: " + prefix + " - value: " + objCrtl.value);
       else
             alert("not found!");
}