Implement an Interface in a standard form via extension

Hello together,

in order to make a standard list page capable of reacting on custom tile filters, I need to implement two interfaces in a standard form (e.g. "SalesQuotationListPage"):

SysIFilterConsumerForm, SysIFilterEventHandler

How could I achieve this?

In the extension class it is possible to add the required methods but an interface is not allowed to be implemented:

[ExtensionOf(formStr(SalesQuotationListPage))]
final class SalesQuotationListPage_Extension
{
    public void registerDatasourceOnQueryingEvent()
    {
        SalesQuotationTable_ds.OnQueryExecuting += eventhandler(this.parmFilterFormQueryEventHandler().applyFilter);
    }

    public void onFilterChanged()
    {
        SalesQuotationTable_ds.executeQuery();
    }

}

The customization is based on the following very helpful blog:

http://www.enavate.com/the365blog/microsoft-dynamics-365-filtering

Thanks in advance for any ideas.

Sebastian

SysIFilterConsumerForm, SysIFilterEventHandler