The HDF_VG_GETNEXT function returns the reference number of the next object inside a VGroup in an HDF file. If Id is -1, the first item in the VGroup is returned, otherwise Id should be set to a reference number previously returned by HDF_VG_GETNEXT.
Result = HDF_VG_GETNEXT(VGroup, Id)
Returns the reference number of the next object or returns -1 if there was an error or there are no more objects after the one specified by Id.
The VGroup handle returned by a previous call to HDF_VG_ATTACH.
A VGroup or VData reference number obtained by a previous call to HDF_VG_GETNEXT. Alternatively, this value can be set to -1 to return the first item in the VGroup.