Maybe this is more like what you were looking for? If gets the list of available drawing standard styles, then presents that to you, and asks you to choose one. Afterwards it confirms that a selection was made, then sets that style as the 'active' standard style.
Dim oDDoc As DrawingDocument = ThisDrawing.Document
Dim oSStyles As New List(Of String)
For Each oSS As DrawingStandardStyle In oDDoc.StylesManager.StandardStyles
oSStyles.Add(oSS.Name)
Next
oChoice = InputListBox("", oSStyles, "", "Drawing Standard Styles", "Drawing Standard Styles List")
If String.IsNullOrEmpty(oChoice) Then Exit Sub
Dim oStyle As DrawingStandardStyle = oDDoc.StylesManager.StandardStyles.Item(oChoice)
oDDoc.StylesManager.ActiveStandardStyle = oStyle
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Wesley Crihfield

(Not an Autodesk Employee)