Thank you very much, it works.

I needed it because I'm creating a custom form with several select elements.
The form is used to present a product kit with several options in each section.

A computer with 3 different video cards, 2 screen types, and 5 HD types...
When a user chooses his package and submit the form I'm creating a product kit $node and save it to the database using node_save.

I set the discount property of the items in the product kit and call node_save again. This time it updates the discount.

Then I call uc_product_kit_add_to_cart().

It works well but I create unnecessary product kits in my database.

I wish I could create a temp product kit without writing it to the database. Is it possible?

Thanks