First add discount then costum field price to sell price..

[sand3rr]

Hi,

in my shop i have a custom field with some options these options give a higher price to the sell price.
Like you see in the image..


When i add discount. First the sell price get updated and then the discount comes..
Is it possible to first do the discount and then add the more price?
Otherwise my price isn't right...

I use the "Quantity related price calculation" plugin for the discount.

grtz sander