calculation logic based on selected fields on catalog item

[SLeelaRaR]

in my catalog item I have multiple items(fields) and price for that items as separate fields., (for example: field A : veg biryani., field B: veg biryani price., here I wrote an condition whenever customer selected item then only that item price should be visible)and  I had a discount field & options to that field  like 10%,20%,30% , whatever I selected  those items price should calculate and apply the discount based on discount value to each item individually ., then populate that net total.(for example I selected 2 items, price is 200,300 ., here I want to apply discount to each item separately.).
can you give me the suggestions/codes to achieve this scenario.

[JenniferRah]

I would put your item list in a custom table. Then in the form, use a Multi-Row Variable Set to allow the user to select an item from the table and enter the quantity. You can calculate the line item price. Then you can have a variable in the catalog item that goes through the MRVS and calculates the total price.