Programming Reference Manual
 
Syntax
 
Dim [WithEvents] name[type][([dim[, ...]])][As [New] type][, ...]
Description
Dimension var array(s) using the dims to establish the minimum and maximum index value for each dimension. If the dims are omitted then a scalar (single value) variable is defined. A dynamic array is declared using  without any dims. It must be ReDimensioned before it can be used. 
See Also
Example
 
Sub DoIt(Size)
    Dim C0,C1(),C2(2,3)
    ReDim C1(Size) ' dynamic array
    C0 = 1
    C1(0) = 2
    C2(0,0) = 3
    Debug.Print C0;C1(0);C2(0,0) ' 1 2 3
End Sub
 
Sub Main
    DoIt 1
End Sub