Limit to List Combo Box

Introduction.

Combo Boxes in tables and forms are used to quickly insert frequently used values into data fields. The source data for a combo box can come from a table, a query, or a value list. To use it, the User clicks the drop-down arrow to display the available options and selects the required value. Alternatively, the user can also type in values directly into the combo box control.

However, one important property setting determines how the combo box behaves:

• The first setting restricts the user to selecting only from the existing list and prevents invalid values in the target field.

• Limit to List = Yes

• On Not in List = [Event Procedure]

When the Limit to List property is set to Yes, you can only select or type values that already exist in the combo box list. Any manually entered values that are not in the list will be rejected. To use a new value, it must first be added to the source table (or query/value list) that supplies data to the combo box.

Example:

Suppose you have a table containing a list of fruits with only two items: Apple and Cherry. This list is used as the source for a combo box on a Sales Form. If the Limit to List property is set to Yes, you cannot type Orange directly into the field. Instead, you must first add Orange to the fruit table; only then will it appear as a valid option in the combo box.

The On-Not-in-List Event.

When the On Not in List Property is set to an Event Procedure, it is executed when the user enters a new value (Orange) manually into the Control-Source Field of the Combo Box. We can write code in the Event Procedure to add the entered new value into the Combo Box Source Table directly (after taking confirmation from the User) and update the Combo Box on the Form.

This method saves the time that would otherwise be spent opening the combo box’s source table and manually adding new items. In addition, values added directly to the source table do not automatically refresh the contents of the combo box.

Let us try this out using the above example items as Source Data.

Combo Box Row Source Table.

1. Create a new Table with a single Field Name: Fruit and select the Data Type Text.

2. Save the Table Structure and name it Fruitlist.

3. Open the Table in Datasheet View and key in Apple and Cherry as two records.

4. Close and save the Table with the records.

5. Create another table with the following Structure:

   Table Structure

   Field Name	Data Type	Size
   ID	AutoNumber
   Description	Text	50
   Quantity	Numeric	Long Integer
   UnitPrice	Numeric	Double

6. Before saving the Structure, click on the second Field Data Type (Text) Column to select it.

7. Click on the Lookup Tab on the Property Sheet below.

   

   Right-click to open Large Image in New Tab/Window.

   
   

   Combo Box Property Settings.

8. Click on the Display Control Property and select Combo Box from the drop-down control.

9. The Row Source Type Property Value will be Table/Query; if it is not, then select it from the drop-down control.

10. Click on the drop-down control of the Row Source Property and select the Table Fruit list from the displayed list of Tables.

11. Change Column Width Property and List Width Property Values to 1".

12. Change the Limit to List Property Value to Yes.

13. Save the Table Structure with the name Sales.

14. Open the Table in Datasheet View and add a new record with Apple, 100, and 1.5 in Description, Quantity, and UnitPrice Fields, respectively.

15. Close and save the Table with the record.

16. Click on the Sales Table to select it and select Form from the Insert Menu.

17. Create a Form using the Form Wizard in Column Format and save the Form with the name Sales.

    Testing Settings.

18. Open the Sales Form in the normal view.

    Since we have added the Combo Box to the Table Structure, it already appears on the form.

19. Press Ctrl++ (or click on the New Record control on the Record Navigation control) to add a new blank record on the Form.

20. Click on the drop-down control of the Combo Box and you will find the list of fruits: Apple and Cherry in it.

21. But, you Key-in Orange into the Description field and press Enter.

    You will be greeted with the following error message:

    

    Right-click to open Large Image in New Tab/Window.

    If you want to enter the value Orange on the Form, first you must add that item to the Fruit list Table.

22. To add a new item, open the Fruit List table, enter Orange as a new record, and then close the table.

However, this action will not automatically refresh the combo box contents to include Orange in the list. To see the updated value, you must either close and reopen the Sales form or add a command button to the form and write code that requeries the combo box contents.

What we did manually in response to the above error message can be automated by writing a VBA Routine that can be run through the On Not in List Event Procedure. You don't need to close and open the Form to refresh the Combo Box contents either.

Add New Item through VBA

1. Open the Sales Form in Design View.

2. Click on the Description Field to select the Combo Box control.

3. Display the Property Sheet (View -> Properties).

4. Find and click on the On Not in List Property.

5. Select Event Procedure from the drop-down list.

6. Click on the build button (. . .) To open the VBA Module.

7. Copy and paste the following Code into the Module, overwriting the top and bottom Procedure lines already appearing in the Module:

   Private Sub Description_NotInList(NewData As String, Response As Integer)
   Dim strmsg As String, rst As Recordset, db As Database
   
   If Response Then
       strmsg = "Entered Item not in List!" & vbCr & vbCr & "Add to List...?"
         If MsgBox(strmsg, vbYesNo + vbDefaultButton2 + vbQuestion, "Not in List") = vbYes Then
          Set db = CurrentDb
          Set rst = db.OpenRecordset("FruitList", dbOpenDynaset)
          rst.AddNew
          rst![Fruit] = NewData
          rst.Update
          rst.Close
          Me.Description.Undo
          Me.Description.Requery
          Me![Description] = NewData
          Me.Refresh
       End If
       Response = 0
   End If
   End Sub

8. Save and Close the Sales Form.

   Trial Run Program.

9. Open it in a normal view.

10. Now, type the name of any fruit that is not in the Combo Box list (say, Peach) in the Description field.

    You will be greeted with the following Message Box:

    

    Right-click to open Large Image in New Tab/Window.

11. Click the Command Button with the Label, Yes, to add the new item keyed in the Description Field into the Fruit List Table and refresh the Combo Box List automatically.

12. Now, click on the drop-down control of the Combo Box, and you can see that the new item is added to the list and accepted in the Description Field as well.

    

    Right-click to open Large Image in New Tab/Window.

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