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How to Create a Correlated Access Combo Box for VAR_ID and Size

Maira Mehtab Sep 21, 2026 869 views

Question details

The user wants to set up a cascading (correlated) combo box in Microsoft Access to display Size values tied to a specific VAR_ID and automatically include newly added values.

Product: Microsoft Access
Device & OS: not provided
Scenario: Building a database form with dependent dropdown lists for VAR_ID and Size that allow dynamic data entry.
Observed behavior: Needs a method to properly filter the Size combo box based on the selected VAR_ID and use the Not In List event to add new sizes seamlessly.

Before you start

Ensure your Microsoft Access tables are properly backed up before modifying table structures and relationships, and verify that you have Developer permissions to edit form properties and VBA code.

Solution 1Recommended

Normalize Tables and Configure the Correlated Combo Box

Proper database normalization is required before creating a cascading combo box. Set up relationships between VAR_ID and Sizes to filter results accurately.

To make correlated combo boxes function smoothly, your data model must be properly structured. You need to separate your data into dedicated tables and use a junction table to handle the relationship.

Create Required Tables

Design three tables: a 'VAR_ID' table, a 'Sizes' table, and a junction table named 'VAR_ID_Sizes'. Set a composite key consisting of both VAR_ID and Size in the junction table.

Add the First Combo Box

Open your form in Design View. Add a combo box for VAR_ID and bind its Row Source to the VAR_ID table.

Add the Dependent Combo Box

Add a second combo box for Size and bind its Row Source to the VAR_ID_Sizes table.

Filter the Row Source

Modify the Row Source query of the Size combo box to filter by the selected value in the VAR_ID combo box (e.g., add WHERE VAR_ID = [Forms]![YourFormName]![cboVAR_ID]).

Data Integrity: Structuring your tables with a junction table and a composite key ensures data integrity and prevents duplicate entries across your database.

Solution 2

Implement VBA Events for Requerying and New Entries

Use VBA macros in Microsoft Access to refresh the dependent combo box dynamically and allow users to add new sizes on the fly.

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Frequently Asked Questions

Why is my dependent combo box blank when I select a VAR_ID?

This usually happens if the Row Source query of the second combo box isn't referencing the first combo box correctly via the Forms!FormName!ControlName syntax, or if the Requery command is missing in the After Update event of the primary combo box.

What does the 'Not In List' event do in Microsoft Access?

The 'Not In List' event triggers when a user types a value into a combo box that is not currently part of the underlying list. It allows you to run VBA code to automatically add that new item to your source tables on the fly.

Can I use cascading combo boxes without writing VBA?

While you can use simple Access Macros to requery the dependent combo box, handling the 'Not In List' event to dynamically insert new records into junction tables typically requires writing specific SQL and VBA code.

How do I handle composite keys in an Access database?

A composite key involves selecting multiple fields (like VAR_ID and Size) in the Table Design view, then clicking the Primary Key button. This ensures that the specific combination of both values remains unique in your junction table.

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