Counting Unique Names

Hello,

I'm stuck on a problem. Basically, I'm trying to build a formula that will count the unique names in one column where the number assigned to them in an adjacent column is less than or equal to some value. In other words, I want a cumulative sum of how many unique names are in the list. Below is an example table:

Mike 1
Jason 1
Mike 1
Marcus 1
Marcus 2
Jake 2
Mike 2
Nick 2
Jake 3
Mike 3
Harold 3

For this example, the formula should return 3 for a value of 1, 5 for a value of 2, and 6 for a value of 3.

Any help you can give me would be greatly appreciated.