User Defined Variable(編號:1325)

Dear All,
I am having a problem regarding user defined variables:
 
Three user defined variables are used in my program:
-------------------------------------------------------
Type Predicate1 'One-parameter Predicate
  Name As String
  Para1 As String
End Type
 
Type Predicate2 'Two-parameter Predicate
  Name As String
  Para1 As Predicate1
  Para2 As Predicate1
End Type
 
Type Clause
  N As Integer
  Atoms(1 To 10) As ?! 'Here is the problem. Each element in this            'array is either Predicate1 or
            'Predicate2. How should I declare the variable
            'type here?!
  Values(1 To 10) As Integer
End Type
-------------------------------------------------------
Any idea is great appreciated. Thanks.
 
 
   Jesse Rau