Form.BeforeUpdate Event (Access)

The BeforeUpdate event occurs before changed data in a control or record is updated.

Syntax

expression .BeforeUpdate(Cancel)

expression A variable that represents a Form object.

Parameters

Name	Required/Optional	Data Type	Description
Cancel	Required	Integer	The setting determines if the BeforeUpdate event occurs. Setting the Cancel argument to True (–1) cancels the BeforeUpdate event.

Remarks

Changing data in a control by using Visual Basic or a macro containing the SetValue action doesn't trigger these events for the control. However, if you then move to another record or save the record, the form's BeforeUpdate event does occur.

To run a macro or event procedure when this event occurs, set the BeforeUpdate property to the name of the macro or to [Event Procedure].

This event does not apply to option buttons, check boxes, or toggle buttons in an option group. It applies only to the option group itself.

The BeforeUpdate event is triggered when a control or record is updated. Within a record, changed data in each control is updated when the control loses the focus or when the user presses ENTER or TAB. When the focus leaves the record or if the user clicks Save Record on the Records menu, the entire record is updated, and the data is saved in the database.

When you enter new or changed data in a control on a form and then move to another record or save the record by clicking Save Record on the Records menu, the AfterUpdate event for the form occur immediately after the AfterUpdate event for the control. When you move to a different record, the Exit and LostFocus events for the control occur, followed by the Current event for the record you moved to, and the Enter and GotFocus events for the first control in this record. To run the AfterUpdate macro or event procedure without running the Exit and LostFocus macros or event procedures, save the record by using the Save Record command on the Records menu.

BeforeUpdate macros and event procedures run only if you change the data in a control. This event does not occur when a value changes in a calculated control. BeforeUpdate macros and event procedures for a form run only if you change the data in one or more controls in the record.

For forms, you can use the BeforeUpdate event to cancel updating of a record before moving to another record.

If the user enters a new value in the control, the OldValue property setting isn't changed until the data is saved (the record is updated). If you cancel an update, the value of the OldValue property replaces the existing value in the control.

You often use the BeforeUpdate event to validate data, especially when you perform complex validations, such as those that:

• Involve conditions for more than one value on a form.

• Display different error messages for different data entered.

• Can be overridden by the user.

• Contain references to controls on other forms or contain user-defined functions.

Note

To perform simple validations, or more complex validations such as requiring a value in a field or validating more than one control on a form, you can use the ValidationRule property for controls and the ValidationRule and Required properties for fields and records in tables.

A run-time error will occur if you attempt to modify the data contained in the control that fired the BeforeUpdate event in the event's procedure.

Example

The following example shows how you can use a BeforeUpdate event procedure to check whether a product name has already been entered in the database. After the user types a product name in the ProductName box, the value is compared to the ProductName field in the Products table. If there is a matching value in the Products table, a message is displayed that informs the user that the product has already been entered.

To try the example, add the following event procedure to a form named Products that contains a text box called ProductName.

Private Sub ProductName_BeforeUpdate(Cancel As Integer) 
    If(Not IsNull(DLookup("[ProductName]", _ 
        "Products", "[ProductName] ='" _ 
        & Me!ProductName & "'"))) Then 
        MsgBox "Product has already been entered in the database." 
        Cancel = True 
        Me!ProductName.Undo 
    End If 
End Sub

The following example shows how to display a message when a control is empty on a continuous form when a user moves to another record.

Sample code provided by: Bill Jelen, MrExcel.com | About the Contributors

Private Sub Form_BeforeUpdate(Cancel As Integer)
    Dim oContr As Control
    For Each oContr In Me.Detail.Controls
        If IsNull(oContr) = True Then
            If MsgBox(oContr.Name & " is empty", vbOKCancel) = vbCancel Then
                Cancel = True: oContr.SetFocus: Exit Sub
            End If
        End If
    Next oContr
End Sub

The following example shows how to use the BeforeUpdate event of a form to require that a value be entered into one control when another control also has data.

Sample code provided by: The Microsoft Access 2010 Programmer’s Reference | About the Contributors

Private Sub Form_BeforeUpdate(Cancel As Integer)
If (IsNull(Me.FieldOne)) Or (Me.FieldOne.Value =  "") Then
    ' No action required
Else
    If (IsNull(Me.FieldTwo)) or (Me.FieldTwo.Value = "") Then
        MsgBox "You must provide data for field 'FieldTwo', " & _
            "if a value is entered in FieldOne", _
            vbOKOnly, "Required Field"
        Me.FieldTwo.SetFocus
        Cancel = True
        Exit Sub
    End If
End If

End Sub

About the Contributors

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Wrox Press is driven by the Programmer to Programmer philosophy. Wrox books are written by programmers for programmers, and the Wrox brand means authoritative solutions to real-world programming problems.

See Also

Concepts

Form Object Members

Form Object