Extending Microsoft.VisualStudio.TestTools.DataSource.XML

Question

I'm writing data driven unit tests using an Xml datasource in C# VS2008.

Attributes look something like this and everything works awesomely.

    [DeploymentItem("HtmlSchemaUrls.xml")]
    [DataSource("DataSource", "Microsoft.VisualStudio.TestTools.DataSource.XML", "|DataDirectory|\\HtmlSchemaUrls.xml", Microsoft.VisualStudio.TestTools.WebTesting.DataBindingAccessMethod.Sequential, "URL")]
    [DataBinding("DataSource", "URL", "URL_Text", "DataSource.URL.URL_Text")]
    [TestMethod]

I'd like to extend the capabilities of the Microsoft.VisualStudio.TestTools.DataSource.XML datasource, preferrably configurable through App.config. For example, a bool when true I run through all the rows in the Xml file and when false I run through only one.

I do not want to perform this check in the test case itself - I have 1000s of test cases with this requirement.

Any guidance on how to achieve this would be most appreciated.