Magento

We have yearly memberhsip product, if you buy that, you get 10% discount thorughtout hte year.

Now they can buy this and login using their account, the discount rule works.

I am just not able to figure out how to make it work, when they are buying membershp as well any other product. I want to reflect 10% even when they are buying this memberhsip (i.e membership product is in the cart).  If they remove this product, the price goes back to normal.

I tried few things, but so far no success.

Can anyone help please?