hi. am back and i got another problem with this selectionchanged event in datagridview1

i set my datagridview1 to

Selectionmode = fullrowselect

the problem is i got nullreferenceexception error whenever i clicked the column header

so meaning selectionchanged fire when i click the columnheader
since columnheader will have a row value of null
the exception appears

i tried to catch it but ending up in messy situation which the
code i written doesn't run right.

is there anyway to prevent user from clicking column header but it still visible?
but if i do that user cant sort the data right..

Code:
 Private Sub DataGridView1_SelectionChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DataGridView1.SelectionChanged
        '   Dim dtgrdv1row As String
        '   Dim checkrowclick As String
        ' checkrowheaderclick = True
        ' '   If DataGridView1.Rows(0).Selected Then
        '  MsgBox("Colum header")
        '  Else

        disabletextfield()
        '    If DataGridView1.rowhe Then
        Button2.Enabled = False
        Button3.Enabled = True
        Button4.Enabled = True
        Button6.Enabled = True
        Button7.Enabled = True
        '
        '    If DataGridView1.CurrentRow.Cells(0).Value <> vbNull Then

nullreferenceEXCEPTION starts here when i click the column header
        ComboBox5.Text = DataGridView1.CurrentRow.Cells(0).Value 'Tripticket
        'End If
        ComboBox1.Text = DataGridView1.CurrentRow.Cells(2).Value 'trucker
        ComboBox2.Text = DataGridView1.CurrentRow.Cells(3).Value 'plate number
        ComboBox3.Text = DataGridView1.CurrentRow.Cells(4).Value 'Truck Type

        TextBox7.Text = DataGridView1.CurrentRow.Cells(5).Value 'Driver
        TextBox3.Text = DataGridView1.CurrentRow.Cells(6).Value 'Destination
        TextBox6.Text = DataGridView1.CurrentRow.Cells(7).Value 'CustomerName 
        TextBox1.Text = DataGridView1.CurrentRow.Cells(8).Value   'Load
        rmrkstxtbox.Text = DataGridView1.CurrentRow.Cells(9).Value 'remarks






    End Sub
thanks for helping out