Datagrid w/ checkbox: Check All?

I've got a datagrid with a checkbox column. Everything looks good.
I'd like to implement a chcekbox that when checked causes all the
checkboxes in the grid to become checked, and vice versa. Any ideas
on how to do this?

The following code does not work:

Dim iRow As Integer
Dim myView As DataView

myView = grdPersonSearchResults.DataSource
For iRow = 0 To myView.Table.Rows.Count - 1
If grdPersonSearchResults(iRow, 0) Then
grdPersonSearchResults(iRow, 0) = Me.chkCheckAll.Checked
End If
Next iRow

Where column 0 is the checkbox row.

Thanks,
Brian