How to change or add price

[thebuzzman]

Hi All,

 

How can I insert an unspecified value (example: 4) in a field text of an attribute of product and that this value does modify the price of the product in my shopping cart ?

 

Example :

 

X = Product = $100.00

Y = Attribute TEXT price = 1

Z = Customer entry = 4

 

A = Final price in shopping cart = X + ( Z x Y) = $104.00

 

Thanks for your Answer

 

Excuse me for my english, I am french.