As asked before, where this was posted, is the Relationship between the Old Table/New Table a One-to-One or a One-to-Many Relationship?
The former is usually handled by simply adding the new Fields to the original Table.
The latter is normally handled with a Main Form tied to the Table on the One-side of the Relationship, and the Subform tied to the Table on the Many-side of the Relationship.
Trying to base a single Form, without using this scenario, on multiple Tables requires a Query, and a Multi-Table Query is often times Read-Only.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007