XML to select a word (within code snippet)

Question

I have this snippet

<?xml version="1.0" encoding="utf-8" ?>
<CodeSnippets  xmlns="http://schemas.microsoft.com/VisualStudio/2005/CodeSnippet">
<_locDefinition xmlns="urn:locstudio">
    <_locDefault _loc="locNone" />
    <_locTag _loc="locData">Title</_locTag>
    <_locTag _loc="locData">ToolTip</_locTag>
   <_locTag _loc="locData">Default</_locTag>
</_locDefinition>
<CodeSnippet Format="1.0.0">
<Header>
<Title>pastDate</Title>
</Header>
<Snippet>
<Code Language="SQL"><![CDATA[DATEADD(,DATEDIFF(XXX,0,)-20,0)]]>
</Code>
</Snippet>
</CodeSnippet>
</CodeSnippets>

How do I change it so that all of the word XXX is selected ?

Do I need to use either of the tags $selected$ and/or $end$ ?