如何通过局域网中一台机器的IP地址来取得对应网卡的物理地址呢？(50分)

　　我有这们的代码为什么不能实现这种转换呢？是不可以吗？谢谢请指点一下！
function TfrmMain.IPToMAC(IPAdd:string;ISFormat:boolean):string;
var
MacAddr:array[1..6]of byte;
MacAddrLen:ULONG;
retWORD;
begin
MacAddrLen:=sizeof(MacAddr);
ret:=SendARP(inet_addr(pChar(IPAdd)),0,@MacAddr,MacAddrLen);
if ret＝ 0 then
if isformat then
result:=format('%2.2x-%2.2x-%2.2x-%2.2x-%2.2x-%2.2x',[MacAddr[1],MacAddr[2],MacAddr[3],MacAddr[4],MacAddr[5],MacAddr[6]])
else
result:=format('%2.2x-%2.2x-%2.2x-%2.2x-%2.2x-%2.2x',[MacAddr[1],MacAddr[2],MacAddr[3],MacAddr[4],MacAddr[5],MacAddr[6]])
else Result:=('No Ack!');
end;

要看sendarp怎么写的