ACC: How to Display Line Numbers on Subform Records

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The following examples demonstrate how to create and use the sample function GetLineNumber().

How to Create the GetLineNumber() Function

1. Open the sample database Northwind.mdb (or NWIND.MDB in version 2.0).
2. Create a new module and type the following line in the Declarations section if it isn't already there:

   Option Explicit

3. Type the following procedure:
   
   NOTE: In the following sample code, an underscore (_) at the end of a line is used as a line-continuation character. Remove the underscore from the end of the line when re-creating this code in Access Basic.

        Function GetLineNumber (F As Form, KeyName As String, KeyValue)
            Dim RS As Recordset
            Dim CountLines
   
            On Error GoTo Err_GetLineNumber
   
            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!"
                  Exit Function
            End Select
   
            ' Loop backward, counting the lines.
            Do Until RS.BOF
               CountLines = CountLines + 1
               RS.MovePrevious
            Loop
   
         Bye_GetLineNumber:
            ' Return the result.
            GetLineNumber = CountLines
   
            Exit Function
   
         Err_GetLineNumber:
            CountLines = 0
            Resume Bye_GetLineNumber
   
         End Function
   						

The GetLineNumber() function requires the following three parameters:

• The form object on which to place line numbers.
• The name of the unique key field in the subform's underlying table. If the record source does not have a single unique key field, add a field with an AutoNumber data type (or Counter in version 2.0) to the underlying table for this purpose.
• The current key field value.

You could use the following sample expression as the ControlSource property setting of a text box on a subform, given that the subform's underlying table has a field called ID as its unique key field:

   =GetLineNumber(Form,"ID",[ID])
				

How to Use the GetLineNumber() Function

CAUTION: Following the steps in this example will modify the sample database Northwind.mdb (or NWIND.MDB in version 2.0). You may want to back up the Northwind.mdb file, or perform these steps on a copy of the Northwind database.

1. Open the Order Details table in Design view, add the following field to the table, and then save the table:

   Field Name: ID
   Data Type: AutoNumber

   NOTE: AutoNumber is called Counter in version 2.0.
   
   This field will serve as the required single unique field for the table.
2. Open the Order Details Extended query in Design view, add the ID field from the Order Details table to the query grid, and then save the query.
3. Open the Orders Subform form in Design view and add the following text box to the form:

   Name: LineNum
   ControlSource: =GetLineNumber([Form], "ID", [ID])

4. On the View menu (or Edit menu in version 2.0), click Tab Order. Drag the LineNum field from the bottom of the Custom Order list to the top, and then click OK.
5. Save and then close the Orders Subform.
6. Open the Orders form in Form view and move to a record with multiple order line items. Note that the LineNum text box displays the record number for each product in the order.