Updating records programatically to duplicate a column's contents to another newly added column

Updating records programatically to duplicate a column's contents to another newly added column

I have a form where I have added a dummy, hidden single line field that mirrors a lookup field so that I can refer this field from other forms as a lookup. 

This is working. In the report I see an extra dummy column that's identical entries. Unfortunately the older entries have this dummy column empty. Is there a way to automatically populate them?

In something like Excel this would literally be a simple copy paste of one col to another. 

But how can I achieve this in Zoho Creator?