commFX.InBufferCount = 0 ‘读m200——m215
commFX.OutBufferCount = 0
data = "011902"
rw data, 0
Tim = Timer
Do
If Timer > Tim + 1 Then Exit Sub
Loop Until commFX.InBufferCount > 7
recedata = commFX.Input
   commFX.InBufferCount = 0
   v = Len(recedata)
If v = 8 Then
          changehl = ""
     For i = 4 To 2 Step -2
     changehl = changehl +ｍｉｄ（recedata, i, 2)
     Next i
    reced = Val("&H" + changehl)
 For i = 0 To 15
AA = reced And 2 ^ i
If AA = True Then
  MM(200 + i) = True
 Else
  MM(200 + i) = False
End If
Next i
End If

‘’‘’‘’‘’‘’‘’‘’‘’‘’‘’‘’‘’‘’

我想知道   changehl = ""
     For i = 4 To 2 Step -2
     changehl = changehl +ｍｉｄ（recedata, i, 2)
这三句是什么意思，有那位高手知道的呀，请指教下