Edit: The original premise of the question was incorrect so revised the question:
Basically I want a button to be visible only when the mouse is over the containing user control. Here is the simplified versin of what I have:
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="MyNamespace.MyUserControl"
x:Name="myUserControl">
<Textbox>Some Text</Textbox>
<Button Visibility="{Binding ElementName=myUserControl, Path=IsMouseOver, Converter={StaticResource mouseOverVisibilityConverter}}" />
</UserControl>
Which works if the mouse is over the text box, but not anywhere else in the user control.