A (temporary) button does the work for us here

How it works

1. Open the Table Settings of the Invoice Items table.
2. Add the layout field Button.
3. Open the Field Settings and enter the following script under On Click:

for i in select Invoice Items do
    i.UnitPrice := i.'Food & Drinks'.UnitPrice
end

Learn more about for ... in ... do ... end and select in our Introduction to Ninox Scripting.

By clicking the Button, the missing unit prices will be assigned to the invoice items. Our first invoice is now complete again.

If you want, you can delete the Button afterward.

Now let's create a new invoice with lots of champagne at the current prices. You will see that everything is working (again)!

Watch the process

https://share.ninox.com/xo1ywprgufy8k2234tzowjw4it5ujkkggdtt?video

This is how you reassign the "disappeared" prices using a button