Adding multiple series to a graph

[p.douglas]

Hi,
I'm quite new to VB and I've gotten stuck with this particular problem, despite several internet searches!

I have two columns of data, I'm trying to add the first 7 rows as series one, and the next 7 as series two etc. until I run out of data. I've tried to write some code but it doesn't work:

[VBA]Dim a As Integer
Dim x As Integer

Sub Graph()
x = 1
a = 1

Do

ActiveSheet.Shapes.AddChart.Select
ActiveChart.ChartType = xlXYScatter
ActiveChart.SeriesCollection.NewSeries
ActiveChart.SeriesCollection(1).Name = "=""x"""
ActiveChart.SeriesCollection(1).XValues = "='Met1'!$B$a:$B$a+6"
ActiveChart.SeriesCollection(1).Values = "='Met1'!$C$a:$C$a+6"

x = x + 1
a = a + 7

Loop Until a = 456

End Sub
[/VBA]

Can anyone help? I would appreciate any pointers with this one as it would take me days to do this 'by hand'

Many thanks
Philippa