x =  Sum(1,2,3)
y =  Sum(1,2)

Function Sum('how to declare argument here')
'Is there any special argument manipulation inside function before it is usable?
End Function

Function Sum(ParamArray Vals() As Variant)
    Dim intLoopIndex As Integer
    For intLoopIndex = 0 To  UBound(Vals)

    Next intLoopIndex

End Function