Microsoft KB Archive/136123

= ACC: How to Use a Bound Control to Find a Record (95/97) =

Article ID: 136123

Article Last Modified on 1/19/2007

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APPLIES TO


 * Microsoft Access 95 Standard Edition
 * Microsoft Access 97 Standard Edition

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This article was previously published under Q136123



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



SUMMARY
This article shows you how you can use a single, bound control for both finding records and for entering data in a form. You can use this technique to find whether the value entered in a field already exists in another record. If the value does exist in another record, the record containing that value is displayed. If the value does not exist in another record, you can continue entering data for the current record.

This article assumes that you are familiar with Visual Basic for Applications and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information about Visual Basic for Applications, please refer to your version of the "Building Applications with Microsoft Access" manual.



MORE INFORMATION
The Microsoft Access online Help system demonstrates how to use the Combo Box Wizard to find records in your database by selecting a key value from a list. (See "Value List," and then "Finding a Record by Selecting a Value from a List" in the Microsoft Access Help system.) 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 for both finding records and for entering data in a form, follow these steps:  Open the sample database Northwind.mdb.  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   Open the Customers form in Design view, and set the properties for the Customer ID control as follows:   BeforeUpdate: =Find_BeforeUpdate(Form) OnExit: =Find_OnExit  View the Customers form in Form view. In the CustomerID control, type "AROUT" (without the quotation marks), and then press ENTER. Note that Microsoft Access finds and displays the Around The Horn customer. In the Customer ID control, type "POPSI" (without the quotation marks), and then press ENTER. Because this key value does not exist, you can continue entering data for the record.</ol>

How the Sample Functions Work
The Find_BeforeUpdate function uses the FindFirst method to search the recordset that the form is based on to see if the value entered 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.

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