You can implement RapidSpellDialog checking in a DataGridView by iterating through the cells yourself.

Eg. (a menu item click handler)

Private Sub SpellDialogToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SpellDialogToolStripMenuItem.Click
        RapidSpellDialog1.Modal = True
        RapidSpellDialog1.ShowFinishedBoxAtEnd = False

        Dim row As DataGridViewRow
        Dim cell As DataGridViewCell

        For Each row In dataGridView1.Rows
            For Each cell In row.Cells
                dataGridView1.CurrentCell = cell
                dataGridView1.BeginEdit(False)
                If TypeOf dataGridView1.EditingControl Is TextBoxBase Then
                    RapidSpellDialog1.TextBoxBaseToCheck =CType(dataGridView1.EditingControl, TextBoxBase)
                    RapidSpellDialog1.Check()
                End If
            Next
        Next
    End Sub