Custom Promotion additional field

Hello everyone,

I’m absolutely new in EpiCommerce. 

I’m using Quicksilver project.

I created my own custom promotion and custom promotion processor as well.

I included 50% percent discount to women handbags (for ex) and it works fine. 

So in addition I have DisountedItem boolean property in my FashionVariant class. I also added metafield and added this metafield to appropriate metaclasses. 

My question is for ex. after using my custom promotion, how to create functionality for checkbox discountedItem

for removing also adding promotion to product manually. 

P.S. as I added metafield and this checkbox ( DiscountedItem) showing in Cms Edit mode. I need just functionality. 

Any suggestions will help me. 

Thanks in advance to everyone.