Dia2017 dialog radiobutton

Hi,

im creating a dialog box, i added radiobutton (rbTest) with one default item.

But when i want to add some items i got and error "Do not modify this list with Remove or Add.".

With combobox it works fine, but here i got error.

Should i do something different with the radiobuttons?

im using add function

Call rbTest.Items.Add("New item", 1)

diadem 2017 (17.0.0f6657) 64bit, win7 sp1