Option Explicit
Type SECURITY_ATTRIBUTES
        nLength As Long
        lpSecurityDescriptor As Long
        bInheritHandle As Boolean
End Type

Type DCB
        DCBlength As Long
        BaudRate As Long
        fBinary As Long
        fParity As Long
        fOutxCtsFlow As Long
        fOutxDsrFlow As Long
        fDtrControl As Long
        fDsrSensitivity As Long
        fTXContinueOnXoff As Long
        fOutX As Long
        fInX As Long
        fErrorChar As Long
        fNull As Long
        fRtsControl As Long
        fAbortOnError As Long
        fDummy2 As Long
        wReserved As Integer
        XonLim As Integer
        XoffLim As Integer
        ByteSize As Byte
        Parity As Byte
        StopBits As Byte
        XonChar As Byte
        XoffChar As Byte
        ErrorChar As Byte
        EofChar As Byte
        EvtChar As Byte
End Type

Type COMMTIMEOUTS
        ReadIntervalTimeout As Long
        ReadTotalTimeoutMultiplier As Long
        ReadTotalTimeoutConstant As Long
        WriteTotalTimeoutMultiplier As Long
        WriteTotalTimeoutConstant As Long
End Type

Type COMSTAT
        fCtsHold As Long
        fDsrHold As Long
        fRlsdHold As Long
        fXoffHold As Long
        fXoffSent As Long
        fEof As Long
        fTxim As Long
        fReserved As Long
        cbInQue As Long
        cbOutQue As Long
End Type

Type OVERLAPPED
        Internal As Long
        InternalHigh As Long
        offset As Long
        OffsetHigh As Long
        hEvent As Long
End Type

Public Const OPEN_EXISTING = 3
Public Const READ_CONTROL = &H20000
Public Const FILE_READ_DATA = (&H1)
Public Const FILE_READ_ATTRIBUTES = (&H80)
Public Const FILE_READ_EA = (&H8)
Public Const SYNCHRONIZE = &H100000
Public Const FILE_WRITE_DATA = (&H2)
Public Const FILE_WRITE_ATTRIBUTES = (&H100)
Public Const FILE_WRITE_EA = (&H10)
Public Const FILE_APPEND_DATA = (&H4)
Public Const STANDARD_RIGHTS_READ = (READ_CONTROL)
Public Const STANDARD_RIGHTS_WRITE = (READ_CONTROL)
Public Const FILE_GENERIC_READ = (STANDARD_RIGHTS_READ Or FILE_READ_DATA Or FILE_READ_ATTRIBUTES Or FILE_READ_EA Or SYNCHRONIZE)
Public Const FILE_GENERIC_WRITE = (STANDARD_RIGHTS_WRITE Or FILE_WRITE_DATA Or FILE_WRITE_ATTRIBUTES Or FILE_WRITE_EA Or FILE_APPEND_DATA Or SYNCHRONIZE)
Public Const CBR_9600 = 9600
Public Const ONESTOPBIT = 0
Public Const NOPARITY = 0
Public Const GENERIC_READ = &H80000000
Public Const GENERIC_WRITE = &H40000000

Public Declare Function CreateFile Lib "Kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, lpSecurityAttributes As Any, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As Long
Public Declare Function CloseHandle Lib "Kernel32" (ByVal hObject As Long) As Long
Public Declare Function GetCommState Lib "Kernel32" (ByVal nCid As Long, lpDCB As DCB) As Long
Public Declare Function SetCommState Lib "Kernel32" (ByVal hCommDev As Long, lpDCB As DCB) As Long
Public Declare Function SetCommTimeouts Lib "Kernel32" (ByVal hFile As Long, lpCommTimeouts As COMMTIMEOUTS) As Long
Public Declare Function ClearCommError Lib "Kernel32" (ByVal hFile As Long, lpErrors As Long, lpStat As COMSTAT) As Long
Public Declare Function ReadFile Lib "Kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, ByRef lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As Long
Declare Function GetLastError Lib "Kernel32" () As Long

Sub SerialTest()
   Dim overlapStruct As OVERLAPPED
   Dim status As Boolean
   Dim result, commError As Long
   Dim comStatus As COMSTAT
   Dim comPortHandle As Long
   Dim dcbSerialParams As DCB
   Dim timeouts As COMMTIMEOUTS
   Dim k As Long
   Dim readData() As Byte
   Dim bytesRead, bytesReadTotal As Long
   Dim chipId As String
   Dim errorCode As Long
   Dim chipsRead As Long
   ' Open COM port.
   comPortHandle = CreateFile("COM3", GENERIC_READ Or GENERIC_WRITE, 0, Null, OPEN_EXISTING, 0, 0)
   If comPortHandle = Null Then
      Call MsgBox("Cannot open COM port")
   End If
   On Error GoTo CleanUp ' Close port if anything goes wrong.
   ' Set COM port parameters.
   dcbSerialParams.DCBlength = LenB(dcbSerialParams)
   status = GetCommState(comPortHandle, dcbSerialParams)
   If status = False Then
      Call MsgBox("Cannot get COM port status data.")
      GoTo CleanUp
   End If
   dcbSerialParams.BaudRate = CBR_9600
   dcbSerialParams.ByteSize = 8
   dcbSerialParams.StopBits = ONESTOPBIT
   dcbSerialParams.Parity = NOPARITY
   status = SetCommState(comPortHandle, dcbSerialParams)
   If status = False Then
      Call MsgBox("Cannot set COM port status data.")
      GoTo CleanUp
   End If
   ' Set time-out values.
   timeouts.ReadIntervalTimeout = 50
   timeouts.ReadTotalTimeoutMultiplier = 1
   timeouts.ReadTotalTimeoutConstant = 10
   timeouts.WriteTotalTimeoutConstant = 0
   timeouts.WriteTotalTimeoutMultiplier = 0
   status = SetCommTimeouts(comPortHandle, timeouts)
   If status = False Then
      Call MsgBox("Cannot set COM time-out values.")
      GoTo CleanUp
   End If
   ' Read tags.
   chipsRead = 0
   While chipsRead < 10
      bytesReadTotal = 0
      Do
         readData() = "InsertSomeUsefulInformationHere"
         status = ReadFile(comPortHandle, readData(0), 12 - bytesReadTotal, bytesRead, 0&)
         bytesReadTotal = bytesReadTotal + bytesRead
         DoEvents
      Loop While bytesReadTotal < 12
      chipId = ""
      For k = 0 To 7
         chipId = chipId + Chr$(readData(k))
      Next k
      Application.ActiveSheet.Cells(chipsRead + 1, 1) = chipId
      chipsRead = chipsRead + 1
   Wend
CleanUp:
   Call CloseHandle(comPortHandle)
End Sub