Add a filter to my report

[Gigatech]

Hi, I use D7. I have two tables: customers and departments. I want to make a "customers by department" report, but I want to choose the department before I generate the report.

I want to add a ComboBox dialog that shows:

All Departaments
Department 1
Department 2
...

(Notice the first item does not exist in the department table)

Which type of control do I have to use?

Thanks