Unable to Set Plotter ConfigName

On a dialog box I have a drop down list of all plot configurations in a drawing. When I select the Printer from a dialog box this value is stored in cboPrinter.value. I then use a Select Case statement to define which value is selected and then run the plot accordingly:

 
   Set plotObj = ThisDrawing.Plot
   Set objLayout = ThisDrawing.ActiveLayout
   Set PlotConfigurations = ThisDrawing.PlotConfigurations
   On Error Resume Next
   objLayout.CopyFrom PlotConfigurations.Item(cboPrinter.Value)
   Select Case cboPrinter.Value
   Case "Piping BW - B-size 11x17"
       objLayout.RefreshPlotDeviceInfo
       objLayout.ConfigName = cboPrinter.Value
       objLayout.PlotType = acExtents
       objLayout.UseStandardScale = True
       objLayout.StandardScale = acScaleToFit
       objLayout.PlotRotation = ac90degrees
       objLayout.CanonicalMediaName = "11x17"
       objLayout.PlotWithPlotStyles = True
       objLayout.StyleSheet = cboPlotStyle.Value
       plotObj.PlotToDevice
    End Select

The problem I'm having is that the line objLayout.ConfigName = cboPrinter.value is not setting the config name. Does anyone have an idea why I can't set the ConfigName?