Why isn't my Wix Property being evaluated?

I'm trying to simulate the InstallURL property of a VS.net install MSI... I've got to the ponit where the WIX MSI will open a browser to the download page that I want it to go to. I thought things were going great because on my test machine, the web page opened when I didn't have the MSXML6 component installed. However things went downhill when I discovered that the web page opened even when I DID have the component installed.

I'm searching for the MSXML6 component using a Property w/ a RegistrySearch. However, as best as I can tell, the registry value isn't even being evaluated, and thus it "always" looks like it isn't installed.

Here's the relevant portion of my WXS:

    <Property Id="MSXML6">
        <RegistrySearch Id="MSXML6Search" Root="HKCR" Key="Msxml2.DOMDocument.6.0" Type="raw" />
    </Property>
    <Property Id="TEST">
        <RegistrySearch Id="TESTSearch" Root="HKLM" Type="raw" Name="Version" Key="SOFTWARE\Microsoft\DirectX" />
    </Property>
    <Property Id="cmd.exe" Value="cmd.exe" />
    <CustomAction Id="OpenMSXML6Download" Property="cmd.exe" ExeCommand="/c start http://www.microsoft.com/downloads/details.aspx?FamilyID=993c0bcf-3bcf-4009-be21-27e85e1857b1" Execute="immediate" Return="check" />
    <CustomAction Id="OpenMSXML6DownloadError" Error="This component requires MSXML6. =[MSXML6]=[cmd.exe]=[TEST]=  A web browser has been opened to the download page.  Please install MSXML6 and then re-install the connector." />

    <!-- installation execution sequence -->
    <InstallExecuteSequence>
        <!-- wires the error dialog to the downgrade event -->
        <Custom Action="PreventDowngrading" After="FindRelatedProducts">NEWPRODUCTFOUND</Custom>

        <!-- execution to delete old install info after upgrade-->
        <RemoveExistingProducts After="InstallValidate" />

        <!-- Forces MSXML6 to be pre-installed -->
        <!-- <Custom Action="OpenMSXML6Download" Before="FindRelatedProducts">NOT MSXML6</Custom> -->
        <Custom Action="OpenMSXML6Download" Before="FindRelatedProducts">NOT MSXML6</Custom>
        <Custom Action="OpenMSXML6DownloadError" After="OpenMSXML6Download">NOT MSXML6</Custom>
    </InstallExecuteSequence>

    <!-- ui information for the custom actions above. -->
    <InstallUISequence>
        <Custom Action="PreventDowngrading" After="FindRelatedProducts">NEWPRODUCTFOUND</Custom>
        <Custom Action="OpenMSXML6Download" Before="FindRelatedProducts">NOT MSXML6</Custom>
        <Custom Action="OpenMSXML6DownloadError" After="OpenMSXML6Download">NOT MSXML6</Custom>
    </InstallUISequence>

What this does is if MSXML6 isn't defined then it opens the web page and then prints the custom error message. Note that I'm trying to print the value of the property in the error message (I'm not sure if this is valid or not, but it seems to be.) The text that I see says "This component requires MSXML6. ==[cmd.exe]==..." so it is printing the value of the 'cmd.exe' property but not the other two... maybe that's because I define the property explicitly, I'm not sure... Anyway, I also ran the MSI with debugging on, and in the log file, I see absolutely no reference at all to the MSXML6 or the TEST properties ever being set. I've confirmed that the registry values are indeed set, although I'm not 100% sure how to handle the Msxml2 registry key, since it doesn't have any real values, only a default value. (I'm assuming that leaving off the 'Name' parameter is the right way to handle this.)

Help??

I managed to figure this one out... it was quite a simple answer. Basic issue was that the Custom Actions were executing before AppSearch, which is where the RegistrySearch properties get evaluated. See my blog post at CTICoder for details.