Dynamically change product price field

Hello,

Using gravity form product field type, I would like to dynamically change the price field depending the quantity field. For example :

if the user type 10 in the quantity field, price may become 1 €. If the user type 20, price become 2 €, ... I need to dynamically set price depending on quantity value.
I saw this link without real answer :
http://www.gravityhelp.com/forums/topic/change-price-product-field-amount-according-to-quantity-discounts

The grid that fix price depending the quantity range can be long (arround 50 lines)

I'm a beginner in gravity form with some knowledge in PHP. What is the best way to do that. Can it be done with some hook ?

Thanks.

Thanks for answer,

I would like to create a form for "work request". User can choose a product from lookup list and it can be 50 base product * 10 or more different quality. For this, I think I can populate a drop down (for different quality) depending on parent choice using hook (gform_pre_render).

Each product and quality have different price depending of the quantity.
There are 4 quantity range :
From 1 to 10, from 11 to 100, from 101 to 500, and from 501 and more. So they are only 4 prices break but arround 4*50*10 different price.

The quantity field must be freely typed (without drop down) because they are too many choice for a dropdown list.

For now, I'm learning gravity form and would know if I can do this with gravity form without using advanced jquery programming. If yes, I want to know where is a good starting point, what is the best way to do this (conditional logic, allow dynamic content update, hook).