Set and keep discount percentages after updates

With over a hundred products I like to keep the prices up date by updating them automatically overnight with Alidropship. The problem is that some shops at AliExpress haven't defined the discount field, so it's set to zero. I can set this myself in AliDropship for my customers, but every night it's reset again to zero (or whatever setting the particular shop at AliExpress is using or failing to use).

Please implement a simply on/off box in the menu for people that want to set the discount percentage (or keep the basic price that they have set themselves). Sale price (adjusted with your own the mark-up) comes from the shop at AliExpress, but any customization to the price field you should be able to keep. The best would be to set and keep the discount percentage, but just keeping the price field fixed would help. This should be pretty quick to implement in the next update.