First, your myClass doesn't have a PrintWord method, unless there is extra code in there your not showing us. Also, from the code you have shown us, myClass is a keyword and can't be used as the name of a class. Plus, your class can be greatly simplified like this:
Public Class testClass
Public Function add(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
Return num1 + num2
End Function
End Class
Second, we need to see line 60 of Form1.vb and the code surrounding it to be able to tell you what is going on. RageInTheMachine9532