Need custom text option in dropdown that doesnt replicate in text field

The calculation script overrides custom entry in the ID field because it runs every time any field on the form is changed. So, the first thing to do is remove the calculation script.  The next thing to do is to add a custom validation script to the dropdown.  The Validation script is only run when the field value is changed. 

This script needs to detect when the entered data is a custom entry, and when it is a selection from the list, then it can determine whether or not the  ID value needs to be updated from the dropdown or cleared for custom entry. 

To do this the item value will need to be searched. 

Enter this script into the Custom Validation Script on the DropDown.

Also, replace the "ORCID" text with the real name of the ID field on your PDF. 

var oIDField = this.getField("ORCID");
var bFound = false;
for(var i=0;i<event.target.numItems;i++)
{
   if(event.target.getItemAt(i,false) == event.value)
   {// Field value is in list, set ID
       oIDField.value = event.target.getItemAt(i,true);
       oIDField.readonly = true;
       bFound = true;
       break;
   }
}
if(!bFound){
  // Field value is not in list, clear ID
   oIDField.value = "";
   oIDField.readonly = false;
}