I figured out the solution:

Public Sub RecordPercentDone(ByVal sender As Object, ByVal
e As System.EventArgs)
Dim ed As DropDownList = CType(sender, DropDownList)
Dim myDatGridItem As DataGridItem = CType
(ed.Parent.Parent, DataGridItem)

Dim projDetailID As String = myDatGridItem.Cells(0).Text
Dim PercentComplete As String = ed.SelectedItem.Text
Do Update......
end sub