What is the great wisdom in defining your own object if I can't do this?

Answer 1

Hint: use "SET".

(most common error made by VB programmers in VB6 and VBA).

Answer 2

Anyway, I don't find that very elegant.
I would rather write:

Function GetBondPrincipal()
   Dim b As BondClass
   Set b = New BondClass
   with b
     .param1 = 0.03
     .param2 = 100
     .InitializeBond
     GetBondPrincipal = .GetPrincipal()
   end with
End Function