I have two cells one is a radiobtnlist with 3 items pass, fail, NA
values of 1, 2, 3

i need to verify that if fail(2) is clicked that another cel text box txtcomm has some data (len > 0)
I keep getting an error that object not set to an instance

here is my code

Public Function chkPFNA_COMM()


        Dim mystring As String
        Dim i As Integer = 0
        Dim x As TextBox
        Dim dgi As DataGridItem

        For Each dgi In dgPrep.Items
            Dim id As Integer = Convert.ToInt32(dgPrep.DataKeys(dgi.ItemIndex))
            Dim txtR_C As String = CType(dgi.FindControl("r_c"), TextBox).Text
            Dim txtPFNA As String = CType(dgi.FindControl("btnPFNA"), RadioButtonList).SelectedValue
            Dim txtCorr As String = CType(dgi.FindControl("chkcorr"), CheckBox).Checked

            If txtPFNA = "2" Then
                errPFNA.Text = "must supply failure"
                chkPFNA_COMM = False
                Exit Function
            End If


        Next
    End Function

What line is the error on?