trying to update _hickashop_product.product_id col

Hi,
I'm using Chronoforms as an interface for users to add products to the system, but I can't seem to update the "product_id" column in the hickashop_product columns. I can update any other column in that table (and in the other tables that are affected when a product is added...)


Here's the prob - If I remove the field that updates "product_id" from my form, all works well and I get the following query (from Joomla debug info...):

UPDATE `jos_hikashop_product`
  SET `product_code`='3000'
  WHERE product_id='3000'

#
UPDATE `jos_hikashop_product`
  SET `product_id`='3000'
  WHERE product_code='3000'

Thanx for your response -

I need users to be able to add their own products.
I have everything worked out so that, when a new product is added, the new product id is populated into the relevant columns -
so, everything's done, I just can't get the hickashop_product.product_id column to update...

It's totally fine if relevant product, etc. don't update as I won't be using that part of the cart.

From my post above:

As soon as add a field in my form that updates the "product_id" column, I get a totally different query in the debug area:


#
UPDATE `jos_hikashop_product`
SET `product_id`='3000'
WHERE product_code='3000'


I can run a query in PhpMyAdmin that updates this column very easily, but for some reason when I try to use chronoforms I get the different query that doesn't work. I've contacted the Chronoforms guys but no solutions - we've been working on this for a few weeks now.