Dynamic default value based on user selection

Hi,

I am using a CF7 form as input for a product-cost-calculator.
The first field of the form is a product selection based on the product-name from the DB.

Later in the form I want to have an attribute of the selected product, which has to be loaded from database to be shown as a default value of an input field to give the user a chance to change it before submission.

So what I need as some kind of an ajax-hook that is changing the input-default-value after changing the product name selection. Something like onChange…

Any idea on how to achieve this with CF7?

Thanks!