WPF chart and DataGrid

Hi All,
Does anyone know how to get the data from a dataGrid into a WPF line series chart (Or other, from the WPF toolkit).

I have my data grid showing data form a dataset in a webservice. I've done that in the code behind:

dataGrid1.ItemsSource = wsCarData.GetSpeed();

Which shows all the data i want in the grid, with the headings etc.

I want to plot that data in the chart, but really don't know where to start.

Any pointers appreciated.

M