Can anyone recommend a procedure for creating large format scaled charts?

Ideally, I'd like the y-axis to have a scale of 5 inches per unit and an
x-axis of 1 inch per 500 units.

Ive used the following macro to set the plot area, but i'd like to automate
it a bit based on data ranges.

Sub ResizePlotArea()
'
' Resize Plot Area Macro
' Macro recorded 6/8/2006 by steve'

'
'Selection.Width =(desired width*72) +36 (36 dependant on axis font)
'Selection.Height =(desired height*72)+25 (25 dependant on axis font)

ActiveChart.PlotArea.Select
Selection.Left = 20
Selection.Top = 108
Selection.Width = 360
Selection.Height = 720
End Sub

Thanks.