Voucher for a list of products

[uzintern]

Hello,
For a list of products (only fifty of them, let's say), how can I create a voucher / coupon? If I use the condition "Valid if a specific product is present in the cart", I can select ONLY one product.
And, if I have two or three vouchers actives (ex: week's offer and winter's offer), how can only one be applicable, if a product is included in both vouchers?