Convert Microsoft Access Tables, Forms, and Reports [Access 2003 VBA Language Reference]
Several changes introduced by Microsoft Access 2002 might affect the behavior of your version 1.x or 2.0 applications. The following sections provide more information about those changes.
Indexes and Relationships
A Microsoft Access table can contain up to 32 indexes. Very complex tables that are a part of many relationships may exceed the index limit, and you won't be able to convert the database that contains these tables. Version 3.6 of the Microsoft Jet database engine creates indexes on both sides of relationships between tables. If your database won't convert, delete some relationships and try again to convert the database.
The LimitToList Property of Combo Boxes
In Microsoft Access 2002 or later, combo boxes accept Null values when the LimitToList property is set to True (–1), whether or not the list contains Null values. In version 2.0, a combo box that has the LimitToList property set to True won't accept a Null value unless the list contains a Null value. If you want to prevent users from entering a Null value by using a combo box, set the Required property of the field in the table to Yes.
Menus and In-Place Activation of OLE Objects
In order to make additional functionality available to you while activating OLE objects in place, some menu commands may have been moved to a menu that isn't replaced when you activate an OLE server.
Macros in your converted application that use a DoMenuItem action to carry out a version 2.0 menu command when a component is activated won't be affected by the changes. Version 2.0 commands are mapped to their equivalents in later versions of Microsoft Access.
Referencing a Control on a Read-Only Form
In Microsoft Access 2002 or later, you can't use an expression to refer to the value of a control on a read-only form that's bound to an empty record source. In previous versions, the expression returns a Null value. Before you reference a control on a read-only form, you should make sure that the form's record source contains records.
Date Fields and Data Entry
If you enter 3/3 in a field of type Date on a form or a table datasheet, the current year is automatically added in Microsoft Access 2002 or later. However, if you enter 3/3/ in the same field, Microsoft Access returns an error message. You must omit the last date delimiter so that Microsoft Access can translate the date into the proper format.
Buttons Created with the Command Button Wizard
If you used the Command Button Wizard in version 2.0 or 7.0 of Microsoft Access to generate code that called another application, you should delete the button and re-create it by using the Command Button Wizard in Microsoft Access 2002 or later.
Form and Report Class Modules
In versions of Microsoft Access prior to 2002, Form and Report objects have associated class modules even if there's no code behind the object. In Microsoft Access 2002 or later, you can set a form's or report's HasModule property to False. When you set the HasModule property to False, the form or report will take up less disk space and will load faster because it will no longer have an associated class module.
Converted Version 2.0 Report Has Different Margins
You may encounter problems when trying to print or preview a report in Microsoft Access 2002 or later that has been converted from Microsoft Access 2.0 if the report has some margins set to 0. When you convert a Microsoft Access 2.0 report, margins aren't set to 0; they are instead set to the minimum margin that's valid for the default printer. This prevents the report from printing data in the unprintable region of the printer.
To resolve this problem, reduce the column width, column spacing, or number of columns in the report so that the width of the columns plus the width of the default margins is equal to or less than the width of your paper.
Can't Use the Format Property to Distinguish Null Values and Zero-Length Strings
In versions 1.x and 2.0, you can use the Format property of a control to display different values for Null values and zero-length strings (" "). In Microsoft Access 2002 or later, to distinguish between Null values and zero-length strings in a control on a form, set the control's ControlSource property to an expression that tests for the Null value case. For example, to display "Null" or "ZLS" in a control, set its ControlSource property to the following expression:
=IIf(IsNull([MyControl]), "Null", Format([MyControl], "@;ZLS"))