You have to use VBA to extract the data. Here's one possible VBA solution: http://peltiertech.com/WordPress/extract-chart-data/. It includes this code:
Sub ExtractChartData()
Dim iSrs As Long
Dim cht As Chart
Dim srs As Series
Dim ws As Worksheet
If ActiveChart Is Nothing Then Exit Sub
Set cht = ActiveChart
Set ws = Worksheets.Add
For iSrs = 1 To cht.SeriesCollection.Count
Set srs = cht.SeriesCollection(iSrs)
On Error Resume Next
ws.Cells(1, 2 * iSrs).Value = srs.Name
ws.Cells(2, 2 * iSrs - 1).Resize(srs.Points.Count).Value = _
WorksheetFunction.Transpose(srs.XValues)
ws.Cells(2, 2 * iSrs).Resize(srs.Points.Count).Value = _
WorksheetFunction.Transpose(srs.Values)
Next
End Sub
Here is another possible solution, direct from Microsoft: http://support.microsoft.com/kb/300643 (Also involves VBA)