wpf - Mahapps metro: How to add an extra button to ShowInputAsync() dialog

Question

In my WPF app I am using MahApps Metro framework. For a test, I am using ShowInputAsync(...) dialog (as shown below) to have user enter product key. I would like to add another button or a link to this dialog so that when a user clicks on that button (or link) the app takes the user to a page that explains how to get a product key. Question: How can we add an extra button or link to Mahapps metro's this input dialog?

private async void BtnEnterProdKey_Click(object sender, RoutedEventArgs e)
{
        var result = await this.ShowInputAsync("Trail Expired:", "Please enter product key and click ok.");

        if (result == null)
            return;
        else
           {
             //code to process product key
           }
}

Current display of the dialog

Answer 1

Waitting for answers