Append Query

I need to at the same time add to 2 tables, append only allows to 1 table

Build 2 Append Queries and use either a Macro or VBA code to run them both.

I tried the 2 append queries, problem is that there is a one to many relationship in the 2 tables, when I append the "One" table, the record that correspond to the "Many" table disappears

When you add a record to the "one" table, there isn't any child record for that entry, so that's why you don't see anything in the "many" table.  That seems like a normal phenomenon.  For instance, on an order form with an order detail subform, if I enter a new order (new record on the "one" side), the subform will be empty because there isn't any order detail yet (no record on the "many" side yet).

Thanks. So how do I fill the the record that I have in the "Many" query which is the subform to the "One"?.

As others have said, you just run another append query to add records to the "many" side.  All primary key fields on the "many" side need to be part of the append, since they don't add themselves.  The appended data need to be actually related to the record on the "one" side, of course.  If the "one" side's ID field is 1, and the appended data to the "many" side also need to have the related ID value of 1.

The record in the "many" side with the same ID as in the "one" side disappears from the many side once I append the records from the "one" side.

It disappears because the "many" side has no records related to the "one" side record you just added.  Every record you add to the "one" side is a DIFFERENT record -- that's why it's called the "one".  There can only be one record on the "one" side that can relate to a specific set of child records on the "many" side.

I found out why it was disappearing, the query that I use to append to tables had a <=Date()-30, so every time I append the "one" with today's date,  it would be gone from the query, so if I don't append the date it works, now the problem is inserting today's date to the record in the "One" table.
I tried through VBA [tblOne]![OrderDate=Date but it does not work.