Testing object type

I was wondering how I could know if an object is an Int or anything else...
I ve got something like this:

Function TestType (o:Object)
     If o isA Int Then
          Return True
     Else
          Return False
     End If
End Function

Well... this is some pseudo code since IsA doesn't exist... but how could I do this?
I ve seen in the doc that to test if an object is of type TImage you do:
If TImage(o) Then
'your code
End If
so I tried doing something like:
If Int(o) Then...
but this return an error like "Unable to convert from object to int"