怎么用OpenRasterDataset加载栅格数据

<P>Public Function OpenRasterDataset(sDir As String, sName As String) As IRasterDataset<BR>  On Error GoTo EH<BR>  Dim pRW As IRasterWorkspace<BR>  Set pRW = OpenRasterWorkspace(sDir)<BR>  Set OpenRasterDataset = pRW.OpenRasterDataset(sName)<BR>EH:<BR>End Function</P>
<P>OpenFromFile我试过了可以的,但是上面的那个程序里面的sName是什么?比如我的栅格数据是:c:\usa\rasterData.jpg,rasterData里面有三个波段:Band_1,Band_2,Band_3,我试了如果把sName设置为rasterData的话报错:未指定的错误.</P>