WParam的“低字”和“高字”位置是否在64位代码中发生变化？

I'm trying to handle the WM_XBUTTONUP message which is from the extra mouse buttons on some mice. The SDK documentation states that the low word of wParam holds the virtual key information and that the high word holds which button was pressed. I understand how this works in 32bit code, however in 64bit code the wParam is a 64bit unsigned integer. I've seen code that uses Lo(msg.wparam) and Hi(msg.wparam). Does this code still work in 64bits or does something have to change? In other words, does the definition of "high word" change from 32bit to 64bit?I'm trying to handle the WM_XBUTTONUP message w