Dropdown Menu Complicated Task with setItems()

Currently using this script in a combo box:

var ITEMS = [[" ", ""], ["ABC"], ["DEF"], ["HIJ"], ["KLM"]];


var DETAILS = [[" ", ""], [123], ["456"], ["789"], ["101112"], ["GO BACK..."];


{

if(event.value == "GO BACK..."){ event.target.setItems(ITEMS)}

if(event.value == "ITEMS") { event.target.setItems(DETAILS);}

}

This works great for what I need.

However, is it possible to also combine the script that @Thom Parker developed :"Using a Combo Box to Pre-populate Form Fields"??

For example

// Place all prepopulation data into a single data structure
var DeptData = { "123":{ contact: "Steala Damuni",
                              email: "accounting@mycomp.com",
                              deptnum: "cmp1234" },
                 "456":{ contact: "Frank N. Stien",
                              email: "engineering@mycomp.com",
                              deptnum: "eng1234" },
                 "789" :{ contact: "Shelly Oughtbuks",
                              email: "marketing@mycomp.com",
                              deptnum: "mkt1234" },
                 "101112":{ contact: "Goah  Wei",
                              email: "it@mycomp.com",
                              deptnum: "its1234" }};

function SetFieldValues(cDeptName)
{
  this.getField("DeptContact").value = DeptData[cDeptName].contact;
  this.getField("DeptEmail").value = DeptData[cDeptName].email;
  this.getField("DeptNumber").value = DeptData[cDeptName].deptnum;
}

I woud like to, somehow, have this second script fill out various text fields once the user selects the second option:

if(event.value == "ITEMS") { event.target.setItems(DETAILS);} from that same dropdown menu.
 

It seems like is not possible.

But I am wondering if upon the combobox populating items when the user selectes this: if(event.value == "ITEMS") { event.target.setItems(DETAILS);}
if that that script can somehow be combined to achieve filling out other texfields employing a single data structure approach.

Is this possible at all?

Could it be this part [" ", ""] ?

I can't figure out how to make these two scripts work together.

Thanks for any help with this.