How can i change the ComboBoxString's WidgetStyle runtime?

I use a ComboBox in page, when the page first construct, will read GameUserSetting and set select option to ComboBox. But this comboBox has been set “Selection Changed Sound”. So that when page first open, the sound will play.I dont want this, so i try to add “Selection Changed Sound” after first open.
In cpp header they said dont direct access WidgetStyle.


So i write a simple tool function like this:
image
And in blueprint:

I am certain that the utility function is running correctly, but nothing happen.When i change the selection, no sound play.