How to automaticaly create a field once previous field is filled

[Guest]

I am trying to create an ivoice form and i want a section that has all the
item of the order. i would like to have it so there is only one field for 1
item originaly and once that field for item 1 is filled then an item 2 field
would automaticaly appear on the form or even have it created in an existing
table and then continue this for item 3 and 4 and so on.

 

[Allen Browne]

This is the wrong way to design this database.
Instead of multiple fields, you need multiple records.

For an example of how to do it correctly, open the Northwind sample database
that comes with Access. Look at the Orders table, and the Order Details
table. One order can have many lines. That's the structure you need.