A long-standing Microsoft Access VBA bug involving conditional formatting has resurfaced in current builds. When more than three FormatConditions are added with acExpression, attempting to access the fourth condition can trigger runtime error 7966 if the expression contains spaces.

The issue was reproduced in Access 2024 Version 2605 and also in the Version 2609 Beta build, showing that it is not limited to one installation or release. A strange but effective workaround is to remove spaces from expressions where possible, such as changing 1 = 1 to 1=1. Another workaround is to create the conditional formatting rules manually in Design View and then modify them with VBA.

The September 2026 Access bug summary reports that the Access team has acknowledged the issue and a fix is expected. This is especially relevant for developers who create or manipulate more than three conditional formatting rules in code.

Sources: Access Bug / Issues Summary - Sept 2026 and Computer Learning Zone discussion and reproduction details.