ACC: How to Use DSum to Create a Running Sum on a Form

MORE INFORMATION

To create a running sum on a form, the underlying table or query must have a unique, sequential, ID field, such as an AutoNumber (or Counter in versions 1.x and 2.0) or a Date/Time timestamp field. If your table does not have such a field, you can open the table in Design view and add a new

field to create one.

NOTE: The following example uses the DSum() function to generate a running sum on a form. For more information on how to generate a running sum on a form by using code, please see the following article in the Microsoft Knowledge Base: The following example uses the sample database Northwind.mdb (or NWIND.MDB in versions 1.x and 2.0) to show you how to create a text box on a form that sums the freight amount for the current customer order and all preceding customer orders:

1. Start Microsoft Access and open the sample database Northwind.mdb (or NWIND.MDB in versions 1.x and 2.0.)
2. Create the following new form based on the Orders table.
   
   NOTE: To improve readability, the underscore (_) is used in the example below as a line-continuation character. Remove the underscore from the end of the line when you are re-creating this example.

         Form:  Form1
         --------------------
         RecordSource: Orders
   
         Text Box: Order ID
            ControlSource: OrderID
         Text Box: Total
            ControlSource: =DSum("[Freight]","Orders",_
                                   "[OrderID] <= Forms![Form1]![OrderID]")
   						

   NOTE: In versions 1.x and 2.0, there is a space in the Order ID field name.
   
   The DSum() function calculates the sum of all freight charges on orders with an Order number less than or equal to the currently displayed order number. For this reason, it is important to have a unique and sequential ID field.
3. View the form in Form view. Note that the Total text box accumulates total freight charges for each order as you move from record to record.