Identify checkbox.checked = True in a datagridview

I have a datagridview that uses a SQL query as the data source.  The last column of the datagridview is a checkbox column.  The code to generate the window is this:

        Dim cmd As SqlClient.SqlCommand = New SqlClient.SqlCommand
        cmd.Connection = cn
        cmd.CommandType = CommandType.Text

        cmd.CommandText = "SELECT ORDER_NUMBER, LINE_NUMBER, QUANTITY, '' AS ADD_WINDOW FROM PCT_PROD_BATCHING WHERE STATUS = 0 ORDER BY ORDER_NUMBER, LINE_NUMBER"
        cmd.CommandTimeout = 0

        Dim dataAdapter As SqlDataAdapter = New SqlDataAdapter(cmd.CommandText, cn)
        dataAdapter.SelectCommand.CommandTimeout = 0
        Dim builder As SqlCommandBuilder = New SqlCommandBuilder(dataAdapter)
        Dim table = New DataTable
        table.Locale = System.Globalization.CultureInfo.InvariantCulture
        dataAdapter.SelectCommand.CommandTimeout = 0
        dgvAddWindow.AutoGenerateColumns = False


        dgvAddWindow.Columns.Add(New DataGridViewTextBoxColumn With {.DataPropertyName = "ORDER_NUMBER", .Name = "Order Number"})
        dgvAddWindow.Columns.Add(New DataGridViewTextBoxColumn With {.DataPropertyName = "LINE_NUMBER", .Name = "Line Number"})
        dgvAddWindow.Columns.Add(New DataGridViewTextBoxColumn With {.DataPropertyName = "QUANTITY", .Name = "Quantity"})
        dgvAddWindow.Columns.Add(New DataGridViewCheckBoxColumn With {.DataPropertyName = "ADD_WINDOW", .Name = "Add Window"})

        dataAdapter.Fill(table)
        AddWindowSource.DataSource = table
        dgvAddWindow.DataSource = AddWindowSource

After selecting rows by checking the checkboxes, and then clicking a Process button, I need to do two things:

1.  Count the number of checkboxes that have been checked.
2.  For each checkbox that has been checked, run some other processes.

I know how to run the other processes, but I don't know how to cycle through the rows and see if the DataGridViewCheckBoxColumn is checked.  Thanks for your help.

T