No answer, so I just set the messagebox parent to the form that's calling Show and just made API calls to recycle the deleted file:
string message = string.Format("Are you sure you want to move '{0}' to the recycling bin?", Path.GetFileNameWithoutExtension(path));
var result = MessageBox.Show(this, message, @"Move To Recycling Bin?", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
if (result == DialogResult.Yes)
{
Send(path, FileOperationFlags.FOF_NOCONFIRMATION | FileOperationFlags.FOF_NOERRORUI | FileOperationFlags.FOF_SILENT);
}
Where the method "send" is part of a wrapper class exposed here