ACC2000: How to Use a Bound Control to Find a Record (210239)

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Microsoft Access online Help demonstrates how to use the Combo Box Wizard to find records in your database by selecting a key value from a list. However, this method is limited in that it is designed to be used with a control not based on any table or query (unbound control). The following example demonstrates how to use a single, bound control to achieve the same functionality.

NOTE: The field to which the control is bound cannot be a required field, and it cannot have a validation rule that allows Null values. Make sure that the field's Required property is set to No, and that its ValidationRule property does not allow Null values.

To use a single bound control both for finding records and for typing data in a form, follow these steps:

1. Start Microsoft Access and open the sample database Northwind.mdb.
2. Create a new module with the following declarations and functions:

   ' *******************************************************
   ' DECLARATIONS SECTION
   ' *******************************************************
   Option Explicit
   Dim Found
   
   
   Function Find_BeforeUpdate (F As Form)
      Dim RS As Recordset, C As Control
      Set C = Screen.ActiveControl
      Set RS = F.RecordsetClone
   
      On Error Goto Err_Find_BeforeUpdate
   
      ' Try to find a record with a matching value.
      Select Case RS.Fields(C.ControlSource).Type
         ' Find using Numeric data type key value?
         Case DB_INTEGER, DB_LONG, DB_CURRENCY, DB_SINGLE, _
         DB_DOUBLE, DB_BYTE
            RS.FindFirst "[" & C.ControlSource & "]=" & C
         ' Find using Date data type key value?
         Case DB_DATE
            RS.FindFirst "[" & C.ControlSource & "]=#" & C & "#"
         ' Find using Text data type key value?
         Case DB_TEXT
            RS.FindFirst "[" & C.ControlSource & "] = """ & C & """"
         Case Else
            MsgBox "ERROR: Invalid data type for '" & C.Name & "'!"
            DoCmd.CancelEvent
            Exit Function
      End Select
   
      ' If a record is found, save the found record's bookmark.
      If RS.NoMatch Then
         Found = Null
      Else
         Found = RS.Bookmark
      End If
   
      ' If the record is found...
      ' ...cancel the BeforeUpdate event
      ' ...undo changes made to the current record
      ' ...and TAB to the next control to trigger the OnExit routine.
      If Not IsNull(Found) Then
         DoCmd.CancelEvent
         SendKeys "{ESC 2}{TAB}", False
      End If
   
      Exit Function
   
   Err_Find_BeforeUpdate:
      MsgBox "ERROR: Err " & Err & ": " & Error$, 48
      DoCmd.CancelEvent
      Exit Function
   
   End Function
   
   Function Find_OnExit ()
      ' If the record is found, cancel the OnExit routine to stay
      ' in the control and go find the record.
      If Not IsNull(Found) And Len(Found) <> 0 Then
         DoCmd.CancelEvent
   
         ' Synchronize the form record with the found record.
         Screen.ActiveForm.Bookmark = Found
   
         Found = Null
      End If
   End Function
   
   					

3. Open the Customers form in Design view, and then set the properties for the Customer ID control as follows:

   BeforeUpdate: =Find_BeforeUpdate(Form)
   OnExit: =Find_OnExit()

4. View the Customers form in Form view. Click the New Record button at the bottom of the form. In the CustomerID control, type AROUT, and then press ENTER.
   
   Note that Microsoft Access finds and displays the Around The Horn customer.
5. Again, click the New Record button at the bottom of the form. In the Customer ID control, type POPSI, and then press ENTER. Because this key value does not exist, you can continue typing data for the record.

How the Sample Functions Work

The Find_BeforeUpdate() function uses the FindFirst method to search the recordset that the form is based on to determine whether the value typed in the control exists in the table.

If the value does not exist, the global variable Found is set to NULL and the function exits. If the value does exist, the global variable Found is set to the bookmark of the found record to be used by the Find_OnExit() function.

Before the found record can be presented, the BeforeUpdate event must be canceled, and a SendKeys action must send two ESC keys to undo changes to the current record.

Next, the SendKeys action sends a TAB key to exit the field. This event triggers the Find_OnExit() function, which checks to see if the find was successful. If it was, the CancelEvent action is run to prevent exiting the control, and then the form record is synchronized with the found record by setting its bookmark equal to the bookmark of the found record. Found is then reset back to NULL.