Adjusting cart price with addJS or $cart->add

[robs113]

VM 2
I am selling a service, the VM product is the generic product with a base price. The final price will be determined in my Joomla component, then an instance of the product is added to the VM2 cart.

I found the addJS call to add the product to the cart but now I need to set/adjust the price.

I tried adding '&adjust_price=123.45' to the addJS call but the product is added without the new price.
Is there a way to add a product to a cart with JS, or php, and set its price also?

Thanks