先定义： #define UM_FIRST (WM_USER + 1)
#define UM_PRIOR (WM_USER + 2)

在程序头文件里定义消息映射：
BEGIN_MESSAGE_MAP
MESSAGE_HANDLER(UM_FIRST, TMessage, UMFirst);
MESSAGE_HANDLER(UM_PRIOR, TMessage, UMPrior);
END_MESSAGE_MAP(TForm);

定义消息函数：
protected:
void __fastcall UMFirst(TMessage Message);
void __fastcall UMPrior(TMessage Message);

函数实现：
//---------------------------------------------------------------------------

void __fastcall TfrmC041::UMFirst(TMessage Message)
{
if (!tblB06->Bof)
{
tblB06->First();
PostMessage(MainHandle, UM_TOFIRST, 0, 0);
}
}
//----------------------------------------------------------------------------

void __fastcall TfrmC041::UMPrior(TMessage Message)
{
if (!tblB06->Bof)
{
tblB06->Prior();
PostMessage(MainHandle, UM_DATASETBROW, 0, 0);
}
else
PostMessage(MainHandle, UM_TOFIRST, 0, 0);
}
//----------------------------------------------------------------------------