How to add part models to Simple representation with vb/Jlink api

I have successfully created new Simple representation. But not able to add part models to it.

My codes are below

Dim newsimRep As IpfcSimpRep

Dim newsimRepInstrs As IpfcCreateNewSimpRepInstructions

Dim newrepname as string="Fix"

Dim solid As IpfcSolid

Dim simRepItem As IpfcSimpRepItem

newsimRepInstrs= (New CCpfcCreateNewSimpRepInstructions).Create(newrepname)

newsimRep = solid.CreateSimpRep(newsimRepInstrs)

'-------

Now I want to add items to this simple representation

Not able to add items to simRepItem

Please guide with codes

Thanks

Gopinath