How do I run Macro associated with Chart

[hill0093]

In the Macro associated with an XYScatter Chart, I use the following Subroutine header to
modify a data point by clicking the point.

Private Sub Chart_Select(ByVal elementTyp As Long, ByVal serID As Long, ByVal pntID As Long)
  If elementTyp = 3 and serID = 1 Then ........

I have another Subroutine that I want associated with the same XYScatter Chart to
be able to run at will. What means do I have to start it in Excel 2003?
I know nothing about this aspect of VBA for Excel.