James,
The range is the first part passed to the chartwizard - see below.
To plot by columns change .plotby = xlRows to .plotby = 2 (which is columns) you can discover the values of the excel constants by using the object browser.
The code below will only work if you have some data in excel - try passing it with _cliptext with the values sepearted by TAB e.g.
_cliptext = "One"+TAB+"Two+CRLF+"Three"+TAB+"Four"
ox.cells(2,2).pastespecial

#DEFINE TAB CHR(9)
#DEFINE CRLF CHR(13)+CHR(10)
ox = CREATEOBJECT('excel.application')
WITH ox.activeworkbook.worksheets(1)
.ChartObjects.ADD(48,720,280,200)
.ChartObjects(2).Chart.Chartwizard(.RANGE(.cells(63,2),.cells(64,49)),xlLine,4,1,0,1,1,"","","","")
WITH .ChartObjects(2).Chart
.hastitle = .T.
.haslegend = .T.
.ChartTitle.CAPTION = "Weekday"
.ChartTitle.FONT.Underline = .T.
.ChartTitle.FONT.Size = 8
.ChartType = 63 && Set a charttype
.plotby = xlRows && Plot by 1 - rows
* Now play with chart format
WITH .Axes(xlValue)
.hastitle = .T.
WITH .AxisTitle
.CAPTION = "Average Demand kWh's"
.FONT.SIZE = 8
.FONT.Bold = .F.
.ORIENTATION = 90 && Show 90 degrees rotated - clockwise
ENDWITH
ENDWITH
WITH .Axes(xlCategory)
.hastitle = .T.
WITH .AxisTitle
.CAPTION = "Half Hours Commencing 00:00 (GMT)"
.FONT.SIZE = 8
.FONT.Bold = .F.
* .Orientation = 90 && Show 90 degrees rotated - clockwise
ENDWITH
ENDWITH
WITH .Legend
.Position = xlLegendPositionBottom
ENDWITH
WITH .SeriesCollection(1)
.NAME = "Summer"
ENDWITH
WITH .SeriesCollection(2)
.NAME = "Winter"
ENDWITH
ENDWITH
ENDWITH

Hope this helps - you should be able to fiddle with it to get the results you need.