How to update "master-detail" selectBoxes for custom properties?

I am trying to figure out a way to set selectOptions for two selectBox, the problem is they are have a master-datail relationship, I must be able to populate the content of the detail to reflect master changes and persist the selected options on the corresponding model Properties . The values to populate selectBox are coming from a database, so for instance, I have these function to retrieve master and detail SelectOptions:

function getMasterOptions(){
  //code to convert retrieved data to array of objects in order to populate SelectOptions  

function getDetailOptions(masterValue){
  //given a masterValue, retrieve corresponding detail options

This is my code so far:

var masterEntry = entryFactory.selectBox({
    id : 'Master',
    label : 'Master',
    selectOptions : getMasterOptions(), //populate master options
    modelProperty : 'Master'

var DetailEntry = entryFactory.selectBox({
    id : 'Detail',
    label : 'Detail',
    selectOptions : // How to do it ?????
    modelProperty : 'Detail'

I know it is all about set and get functions, I saw the examples, but I could not make it work. I really appreciate some help about this.