Automatically adding up cells with corresponding row names

Hi guys,

I have the following problem: I want to add up cells that have a corresponding row name. Because I have a data file that consists of more than 13.000 rows it would save me alot of time if Excel can do this automatically. I presume it's possible but don't know how to do it.

In the attachment you can see what I mean. The numbers in the A column are customer numbers. I want to know what's the total amount spent by each customer, just like the red figures in the c column.

If I would use SPSS for example to create a bar chart of the sum of the amounts spent per customer I would see it graphically, but I need the figures as figures and not as bars!

Who is going to make my day and show me the solution. Thanks in advance for your attention!