用VBA,想看Raster有几个bands，为什么下面的代码会出错

Public Sub checknumber()

Dim pMap As IMap
Dim pMxDocument As IMxDocument
Set pMxDocument = ThisDocument
Set pMap = pMxDocument.FocusMap

Dim pRasterlayer As Irasterlayer
Set pRasterlayer = pMap.Layer

Dim pRaster As IRaster
Set pRaster = pRasterlayer.Raster

Dim pRasBC As IRasterBandCollection
Set pRasBC = pRaster
MsgBox "Number of bands in Raster:" ; CInt(pRasBC.Count)

End Sub

运行后出现compile error:argument not optional的错误，然后指向了Public Sub Checknumber()，请问这个代码有什么问题？？

搞定了，是因为Set pRasterlayer = pMap.Layer应该改成pMap.layer(0)