IGlobalSpeedLimitPtr pSpeedLimit;
if(SUCCEEDED(pSpeedLimit.CreateInstance(__uuidof(sfFTPLib::GlobalSpeedLimit))))
{
    try
    {
        pSpeedLimit->DownloadSpeedLimit = 10 * 1024; // 10 KB/s
        pSpeedLimit->UploadSpeedLimit = 15 * 1024; // 15 KB/s
    }
    catch(...) { }
}

Dim obj
Set obj = CreateObject("sfFTPLib.GlobalSpeedLimit")

obj.DownloadSpeedLimit = 10 * 1024 ' 10 KB
obj.UploadSpeedLimit = 1 * 1024 ' 1 KB