so, the size list should be set to use the sizes_table.Description as the label and sizes_table.Sizes_ID as the value.
you will need to create price lookup recordset to return the price and description for the selected size.
The add to cart form will have a hidden form element for the Item ID, and the Price select list. the names will be similar to:
Cartname_1_ID_Add
Cartname_1_Size_Add
you'll want to chaeck the add to cart form for the correct form element names. These will be used to filter the recoprdset.
The Recordset will be created using Advanced View.
Enter the following query in the SQL window:
SELECT price_table.Price, sizes_table.Description
FROM price_table
INNER JOIN sizes_table ON price_table.Sizes_ID = sizes_table.Sizes_ID
WHERE price_table.Items_ID = cartItem AND price_table.Sizes_ID = cartSize
In the Variables window, create the following 2 variables:
Name: cartItem
Type: Number
Default Value: -1
Run Time Value: $_POST['Cartname_1_ID_Add']
Name: cartSize
Type: Number
Default Value: -1
Run Time Value: $_POST['Cartname_1_Size_Add']
Remember, the names of the form elements may be slightly different, so make sure to use the correct form element names.