I used the following code to make the combobox:

Private Sub Workbook_open()

With Sheet2.ComboBox1

.AddItem "1"
.AddItem "2"
.AddItem "3"
.AddItem "4"
.AddItem "5"
.AddItem "6"
.AddItem "7"
.AddItem "8"
.AddItem "9"
.AddItem "10"
.AddItem "11"
.AddItem "12"

End With

Maybe i did something wrong here?
Besides that i just assigned the combobox to a cell. They still show 1,2..12 in the cells. but they seem useless.