How can I use an optional array argument in a VBA procedure?

Question

I\'ve got a private procedure in a VBA script for MS Access:

Private Sub drawLineDiagram(chartSpace As Variant, title As String, caption As String, x_val() As

Answer 1

The IDE might not be of great use, but the help (for once) contains the answer:
ParamArray
Optional. Used only as the last argument in arglist to indicate that the final argument is an Optional array of Variant elements. The ParamArray keyword allows you to provide an arbitrary number of arguments. ParamArray can't be used with ByVal, ByRef, or Optional.