Check if part is already loaded in session

I'm creating my own "library" Form from where I insert often used parts.

I have a problem with inserting a component when it's already loaded into a session.

For the moment I use Try...Catch. There is a collection of theSession.Parts which I assume I could check somehow if there is already a part which I want to load...
Could you help me with that?

TryDim basePart As BasePart
   Dim partLoadStatus1 As PartLoadStatus
   basePart = theSession.Parts.OpenBase(pfile, partLoadStatus1)
   partLoadStatus1.Dispose()Catch ex As Exception
   lw.writeline(ex.Message) 
EndTry