That's it in the first instance. I will need to do the automatic update later using the loop. But for now if we just crack the manual method.
If I call the column name: colname, the recordset would look like this:
SQL:
SELECT (table.inventory - colname) AS available_inventory
FROM table
WHERE available_inventory > 0
Variables:
Name: colname
Type: Integer
Default value: 0
Run-time: $_POST['<table.inventory>']