Use the GetPOV() method of Joystck to get the current DPad reading. We've used something similar to this in the past::
Code:
switch (m_driveStick.GetPOV())
{
case 0:
// Do Something - the 'up' button
break;
case 90:
// Do Something - the 'right' button
break;
case 180:
// Do Something - down
break;
case 270:
// Do Something - left
break;
default:
break;
}