How to display a non-blocking warning for the operating system in Wix?

Question

I already block installation of our software on operating systems where it is known not to work like this:

<Condition Message="This software needs Windows XP or newer.">
   <![CDATA[VersionNT >= 501]]>
</Condition>

Now I would also like to display a non-blocking warning if the user tries to install the software on an operating system (VersionNT + Service Pack) that is not explicitly supported, even though it might work.

For example, we only explicitly support the latest service pack of each operating system.

How can I display such a warning?