ACC2000: Sample Function to Create a Running Sum on a Form

ID: q210338

The information in this article applies to:

Microsoft Access 2000

Moderate: Requires basic macro, coding, and interoperability skills.

SUMMARY

This article shows you how to create a sample user-defined function to compute a running sum on a form.

MORE INFORMATION

One way to compute a running sum on a form is to use the DSum() function. For additional information about how to use the DSum() function to compute a running sum on a form, please see the following article in the Microsoft Knowledge Base:

Q210495 ACC2000: How to Use DSum to Create a Running Sum on a Form

Using the method demonstrated in this article has the following advantages over using the DSum() function:

The method demonstrated in this article does not require a sequential ID field. A required sequential ID field limits you to computing a running sum using a single ordering of your records.

Using the method demonstrated in this article is significantly faster than using the DSum() function to compute a running sum.

How to Create and Use the RunSum() Function

Microsoft provides programming examples for illustration only, without warranty either expressed or implied, including, but not limited to, the implied warranties of merchantability and/or fitness for a particular purpose. This article assumes that you are familiar with the programming language being demonstrated and the tools used to create and debug procedures. Microsoft support professionals can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific needs. If you have limited programming experience, you may want to contact a Microsoft Certified Solution Provider or the Microsoft fee-based consulting line at (800) 936-5200. For more information about Microsoft Certified Solution Providers, please see the following page on the World Wide Web:

http://www.microsoft.com/mcsp/

For more information about the support options available from Microsoft, please see the following page on the World Wide Web:

http://www.microsoft.com/support/supportnet/refguide/

NOTE: The sample code in this article uses Microsoft Data Access Objects. For this code to run properly, you need to reference the Microsoft DAO 3.6 Object Library.

Open the sample database Northwind.mdb. Create a new module, and type the following line in the Declarations section if it is not already there:


Option Explicit

Type the following code in the module:


Function RunSum (F As Form, KeyName As String, KeyValue, _
  FieldToSum As String)
'***********************************************************
' FUNCTION: RunSum()
' PURPOSE:  Compute a running sum on a form.
' PARAMETERS:
'    F        - The form containing the previous value to
'               retrieve.
'    KeyName  - The name of the form's unique key field.
'    KeyValue - The current record's key value.
'    FieldToSum - The name of the field in the previous
'                 record containing the value to retrieve.
' RETURNS:  A running sum of the field FieldToSum.
' EXAMPLE:  =RunSum(Form,"ID",[ID],"Amount")
'***********************************************************
   Dim RS As DAO.Recordset
   Dim Result

   On Error GoTo Err_RunSum

   ' Get the form Recordset.
   Set RS = F.RecordsetClone

   ' Find the current record.
   Select Case RS.Fields(KeyName).Type
      ' Find using numeric data type key value?
      Case DB_INTEGER, DB_LONG, DB_CURRENCY, _
         DB_SINGLE, DB_DOUBLE, DB_BYTE
         RS.FindFirst "[" & KeyName & "] = " & KeyValue
      ' Find using date data type key value?
      Case DB_DATE
         RS.FindFirst "[" & KeyName & "] = #" & KeyValue & "#"
      ' Find using text data type key value?
      Case DB_TEXT
         RS.FindFirst "[" & KeyName & "] = '" & KeyValue & "'"
      Case Else
         MsgBox "ERROR: Invalid key field data type!"
         GoTo Bye_RunSum
   End Select

   ' Compute the running sum.
   Do Until RS.BOF
      Result = Result + RS(FieldToSum)

      ' Move to the previous record.
      RS.MovePrevious
   Loop

Bye_RunSum:
   RunSum = Result
   Exit Function

Err_RunSum:
   Resume Bye_RunSum

End Function

Create the following new query based on the Orders table and the Order Subtotals query. Save the query as qryOrders:


   Query: qryOrders
   ------------------------------------------------------
   Type: select query
   Join: Orders.[OrderID] <->; [Order Subtotals].[OrderID]

   Field: OrderID
      Table: Orders
      Sort: Ascending
   Field: Subtotal
      Table: Order Subtotals

Use the Form Wizard to create a new form based on the qryOrders query. Include both fields on the form. On the next screen click Tabular.

Add a text box with the following properties to the new form:


   Name: RunningSum
   ControlSource: =RunSum([Form],"OrderID",[OrderID],"Subtotal")
   Format: Currency

Save the form and then view it in Form view.

Select different records using the record selector. Note that the RunningSum field shows an accumulated total based on the Subtotal field.

Additional query words: inf total


Keywords          : kbusage kbdta FmsHowto 
Version           : WINDOWS:2000
Platform          : WINDOWS 
Issue type        : kbhowto

Last Reviewed: May 28, 1999