Auto-Filter Products Based Upon User

I would very much appreciate any clues that someone could give me here.  I need to show special products for each of my customers that the other customers cannot see - basically a different population of products for each customer.  My challenge is that it appears that the product list is being stored in memory and only refreshed when there is an Admin change so I don't know how to be sure that the list is always filtered.

Any comments would be appreciated!

Thank You

OK, I would love to know from the developers how dangerous this is, but I found a simple way to stop the site from Caching so that I could make my changes in SQL.  I'm much more comfortable in SQL than C# and I'm used to applications that put all business logic in SQL so that it can be easily changed behind the scenes.

I changed nop.common/NopContext.cs
as follows:

  public static bool IsCachable
        {
            get
            {
               // return true;
                return false;
            }
        }