Setting the Selected Index of a dropdown list based on a radio button selection

Hi all ..
I have a form with three radio buttons and a drop down list (there are more fields but wanted to simplify the question!) .. based on which radio button is checked, I want to set the selected index of the drop down .. Do i do this on the Onchecked Change event of the radio button or the SelectedIndex change of the dropdown?
Is it as simple as

If radio1.checked then
ddltest.selectedIndex.index = 3
end If
???
 
PS .. it's never that simple  :)

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