how to get dropdown selected value

I'm trying to set up a form so that a text field will populate with dropdown value.

to bind dropdown i am using sqlserver database.

i tried this but it is not working :-

var sNewSel = this.boundItem(xfa.event.newText);

and

var sNewSel = $.boundItem(xfa.event.newText);

this code works if drop down bind eith XML source but does not work if dropdown bind with sqlserver data base

Please help.. Thanks in advance