Array Assign Error

What is wrong with the following code? How do I fix it? I get a a run time error 13 "Type Mismatch" error when I execute.

Option Explicit

Dim S As Variant

Sub Calc1()
    S(1, 1) = 2  
    S(2, 1) = 3
    S(3, 1) = 4
End Sub

Thanks,