Combing comboboxes. Export value empty

Dear all,

Yesterday I started to build a PFD form.

Combobox 1 (Units/company) :

myUnitValues = ["PCH", "TPE"];

On keystroke:

if( event.willCommit )

{

   if(event.value == "")

     this.getField("Unit");

   else

    SetFieldValues(event.value);

}

You can choice between two companies

Combobox 2 (Departments):

var DeptData = {PCH: ["NL Concern Communications","Accounting Europe (NL) ",

"NL Concern Communications",

This works fine, only my export value is empty after the change between the Units.

Textfield 1

In this text field I like to have my export value. This is the cost center of the department.

How can I add in this text field. When department = "NL Concern Communications" then value textfield="12.23.678"

Because my export value disappears after change in Combobox 1

This was working before I added combobox 1  

var cComboBox = "Combobox2";

var sComboBox = this.getField(cComboBox).value; 

event.value = sComboBox;

Can anyone tell me how I can use my text field to make the cost center visible. (read only field)

With kind regards

Mirjam