Sets of pruducts

[Dali10]

Hello,
I'm new in virtuemart world and would like to ask you how to create sets of product. For exmaple:
I have category T-SHIRTS. In this category are products tshirt(5 pieces in stock), blue tshirt(5 pieces in stock), black tshirt(5 pieces in stock), green tshirt(5 pieces in stock),... the same price 10$
I would like to create new product "Set of TSHIRTS", where you are available to choose 2 pieces of product from category T-SHIRTS(red, green, black,...) an total price for this set will be 8$.
And if sombody buy this set (select red and blue), then pieces in stock will be for red 4 and blue 4

Click - Product "Set of TSHIRTS", dropdown menu: firt tshirt , dropdown menu: second tshirt , price 8$, stock available in individual product: -1

Thanks in advance for your help.
Jiri

[Milbo]

Use the multivariants
for the discount you need a plugin https://extensions.virtuemart.net/product/products/quantity-related-price-calculation-detail