A screenshot of the "Custom Column" dialog box within Power Query. The dialog box is set to create a new column named "API Conversion." The formula entered in the "Custom column formula" field is: = Json.Document(Web.Contents("https://api.getthedata.com/bng2latlong/" & Text.From([Easting]) & "/" & Text.From([Northing]))). On the right side of the dialog box, a list of available columns is displayed: "Easting," "Northing," and "Count birds." At the bottom, it indicates that no syntax errors have been detected. Two buttons, "OK" and "Cancel," are visible at the bottom of the dialog.