Given two addresses on a Zoho Creator record — a pickup and a drop-off, a technician and a job site, a warehouse and a customer — the Google Distance Matrix API returns the driving distance between them. This function calls it from Deluge and writes the result back to the record in kilometres or miles, ready for mileage billing, route costing, or delivery-zone rules.

Before you start

• A Google Cloud project with the Distance Matrix API enabled and billing attached. Google’s setup guide walks through key creation.
• A form (called Distance_Calc here) with address fields for both ends: Street/City/State/PostalCode and the matching Street1/City1/State1/PostalCode1.
• Two output fields: textDistance (single line) and Distance (decimal).
• Restrict the API key to the Distance Matrix API in the Google console. A key pasted into a Deluge function is only as safe as the app it lives in.

Deluge function

void API.CalcDistance(int id)
{
    d = Distance_Calc[ID == input.id];

    // Build the origin and destination query strings
    strAddress1 = "origins=" + d.Street + "," + d.City + "," + d.State + "," + d.PostalCode;
    strAddress2 = "&destinations=" + d.Street1 + "," + d.City1 + "," + d.State1 + "," + d.PostalCode1;

    apiKey = "YOUR_GOOGLE_MAPS_API_KEY";
    strFullData = "https://maps.googleapis.com/maps/api/distancematrix/json?" + strAddress1 + strAddress2 + "&key=" + apiKey;

    response = invokeurl
    [
        url  : strFullData
        type : GET
    ];

    // Read the first element of the first row
    rows = response.getJSON("rows");
    if(rows != null && rows.size() > 0)
    {
        elements = rows.get(0).getJSON("elements");
        if(elements != null && elements.size() > 0)
        {
            element = elements.get(0);
            if(element.getJSON("status") == "OK")
            {
                distText = element.getJSON("distance").getJSON("text");   // e.g. "12.4 km"
                distVal  = element.getJSON("distance").getJSON("value");  // metres, integer

                d.textDistance = distText;
                d.Distance = distVal.toDecimal() / 1000;   // km. Use / 1609.34 for miles.
            }
            else
            {
                info "Distance Matrix element status: " + element.getJSON("status");
            }
        }
    }
    else
    {
        info "Distance Matrix error: " + response.toString();
    }
}

Notes

• Two status fields, not one. The top-level response status can be OK while an individual element is ZERO_RESULTS. Check the element status, as above, or you will store zeros for unroutable pairs.
• Metres are the reliable value. distance.value is always metres regardless of locale; distance.text is a formatted string that changes with the units parameter. Convert from the numeric value.
• Coordinates work too. Swap the address strings for origins=lat,lng and destinations=lat,lng if you already geocode.
• Call it on a workflow, not on every edit. Distance Matrix is billed per element. Trigger the function on create, or on a button, rather than on every field change.