Extending Windows Property Handlers with additional properties

Question

I'm using SSLWare's EZShellExtensions.Net v2011 , they support Property Handlers, but the code doesn't work exactly like I want it to work.

I want to add a couple of new properties to the property handler for docx xlsx file extensions, but my code removes all the default ones.

Is there a way to add additional properties with EZShellExtensions? Or do I have to use C++ ?

Example code:

[TargetExtension(".docx", true)]
[TargetExtension(".xlsx", true)]
[TargetExtension(".xlsm", true)] 
public class PropertyHandler4 : PropertyHandler
{

    public PropertyHandler4()
    {
    }

    protected override Property[] GetProperties()
    {
        // TODO : Write your code here.
        // Defines two properties for a file 

        UserDefinedProperty prop = new UserDefinedProperty("MyProperty1");
        prop.Description = "My Property1";
        prop.LabelText = "My Property1";

        UserDefinedProperty prop1 = new UserDefinedProperty("MyProperty2");
        prop1.Description = "My Property2";
        prop1.LabelText = "My Property2";

        return new Property[] { prop, prop1 };
    }

    // Override this method to retrieve the value of the specified property.
    protected override object GetPropertyValue(Property property)
    {
        return "WUZZAP!";
    }