Private Declare Function inet_addr Lib "wsock32.dll" (ByVal s As String) As Long
Private Declare Function SendARP Lib "iphlpapi.dll" (ByVal DestIp As Long, ByVal ScrIP As Long, pMacAddr As Long, PhyAddrLen As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (dst As Any, src As Any, ByVal bcount As Long)

Option Explicit
 
Private Const No_ERROR = 0
 
Private Declare Function inet_addr Lib "wsock32.dll" (ByVal s As String) As Long
Private Declare Function SendARP Lib "iphlpapi.dll" (ByVal DestIp As Long, ByVal ScrIP As Long, pMacAddr As Long, PhyAddrLen As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (dst As Any, src As Any, ByVal bcount As Long)
 
Private Function GetRemoteMACAddress(ByVal sRemoteIP As String, sRemoteMacAddress As String) As Boolean
    Dim dwRemoteIp As Long
    Dim pMacAddr As Long
    Dim bpMacAddr() As Byte
    Dim PhyAddrLen As Long
    Dim cnt As Long
    Dim tmp As String
 
    dwRemoteIp = inet_addr(sRemoteIP)
    If dwRemoteIp <> 0 Then
        PhyAddrLen = 6
        If SendARP(dwRemoteIp, 0&, pMacAddr, PhyAddrLen) = No_ERROR Then
            If pMacAddr <> 0 And PhyAddrLen <> 0 Then
                ReDim bpMacAddr(0 To PhyAddrLen - 1)
                CopyMemory bpMacAddr(0), pMacAddr, ByVal PhyAddrLen
                For cnt = 0 To PhyAddrLen - 1
                    If bpMacAddr(cnt) = 0 Then
                        tmp = tmp & "00-"
                    Else
                        tmp = tmp & Hex$(bpMacAddr(cnt)) & "-"
                    End If
                Next
 
                If Len(tmp) > 0 Then
                    sRemoteMacAddress = Left$(tmp, Len(tmp) - 1)
                    GetRemoteMACAddress = True
                End If
 
                Exit Function
            Else
                GetRemoteMACAddress = False
            End If
        Else
            GetRemoteMACAddress = False
        End If
    Else
        GetRemoteMACAddress = False
    End If
End Function
 
Private Sub btnGetMac_Click()
Dim sRemoteMacAddress As String
If Len(txtIpAddress.Text) > 0 Then
    If GetRemoteMACAddress(txtIpAddress.Text, sRemoteMacAddress) Then
        lblMacAddress.Caption = sRemoteMacAddress
    Else
        lblMacAddress.Caption = "(SendARP call failed)"
    End If
End If
End Sub