How to remove duplicates values from lookup field In nintex forms

Hello Team,

I want to remove duplicates values from lookup filed on nintex forms. I have tried for normal drop down control which contains duplicates in nintex forms. I am able to remove those duplicates values from drop down control.I have used below code for remove duplicates from drop down control.

NWF$(document).ready(function(){
NWF$("#"+txtsite).on('mousedown',function(){
var usednames=[];
$("select[id="+txtsite+"]>option").each(function(){
if(usednames[this.text]){
$(this).remove();
}
else{
usednames[this.text]=this.value;
}
});
});
});

Same code I tried for lookup filed but it's not working for lookup filed. If anyone have any idea about this query. Please help me out.

Thank you,

Santhosh.