All you have to do is create the ScrollViewer in XAML first, making sure you give it a unique name, then create a MarkupScrollViewer object using MarkupUIElement.FindName.

 

For example, you would create the ScrollViewer using XAML like this:

 

<Page xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>

<ScrollViewer VerticalScrollBarVisibility='Auto' HorizontalScrollBarVisibility='Auto' Name='Scroller'></ScrollViewer></Page>

 

And assign this to the control Caption.

 

Then use this to get the ScrollViewer object:

 

Dim pScrollViewer As MarkupScrollViewer
Set pScrollViewer = Me.markupIcons.MarkupContext.CreateObject("ScrollViewer")
Set pScrollViewer = Me.markupIcons.MarkupUIElement.FindName("Scroller")

 

Now you can use the pScrollViewer object as before - but it will now be displayed with a horizontal scroll bar when this is necessary - something you can't reproduce purely from pScrollViewer properties.