Adding selections to combo box with VBA

This should be very easy, but I am not getting it to work. I have a userform with a combo box and I just want to hard code the values to it in VBA. I want the value in the combo box to be 1 - 10. Here is what I have so far.

Private Sub UserForm_Initialize()
With ComboBox1
.AddItem "1"
.AddItem "2"
.AddItem "3"
End With
End Sub

For some reason I cannot get this to work. Any suggestions would be extremely helpful.

Thank You!