The first step is to have the Subtotal or Total field value in the Order Form. Normally this would be a currency field or decimal field if you need to consider 1 or more decimals into your calculations. If not you can also set it the field as a Numeric value field. Our example uses a currency field.

Second you need to think about the places where the script to aggregate the rows needs to occur. in our case there are several places. On Add Row, On Selecting a new Product, On Changing the Qty amount or the pricing. Its important that all scenarios are considered otherwise your calculations may not be properly aggregated if it encounters a scenario that you have not considered in your scripting yet.

To build a robust Order form in zoho creator you need to be able to automatically "fetch" the information about a product and let the system pre populate the subform with pre existing data in the Products Table.

First, you need to have a Products form with all the relevant information about the Product. Price, Description, etc.

Second, you  need to fetch the Product information based "On user input" inside the items Subform and add the below deluge scripting.

prodct  =  Products  [ID == row.Product];
row.Description = prodct.Description;
row.Price = prodct.Price;
row.Qty = 1;
if ((row.Price  !=  null)  &&  (row.Qty  !=  null))
{
    row.SubTotal = (row.Price ...