I have added a customer and given him discount on some products.
How ever it calculate the discount on Price and not List Price.
Some of my products is alredy discountet and i cant give discount on already discountet products.
So how can i make the discount work only with List Price and not Price ?
Jon, the “List Price” is only used as a reference if desired to show your customers the great deal you are offering them, serves no other purpose than as a display.
Any discount calculations are based upon what you have entered in the “Price” field.
To simplify this, you can leave the “List Price” fields entirely blank as they are not even required, they are optional fields! 
The list price for me is useless, bin it if you dont need it and use qty discounts.
John