lookup values in table, return sum of values from first column

Hello,

I'm trying to solve this for days, with no succes.
I've attached a jpeg for making my question more clear.

In the first column (column A6:A11) I have 7 values.
In the table B6:I11there are random numbers.

If I fill in a number in cell B16.
I would like to find a formula (in cell B17) that is looking up that number in the table.
If it finds the exact number, it gives the value in the same row in column A.
If it finds the number more times, all the corresponding values in column A must add up.

I hope someone can help me with this one.


greetz,

Owen