If you set grid.TableStyle.CellType = "OriginalTextBox";, then you will be able to select partical words. This setting changes the default edit control in the cell from a Windows Forms RichTextBox derived control to a Windows Forms TextBox derived control.
If you want to teh default cell type for some reason, then try handling CurrentCellControlGotFocus and set the property there.
this.gridDataBoundGrid1.CurrentCellControlGotFocus += new ControlEventHandler(gridDataBoundGrid1_CurrentCellControlGotFocus);
private void gridDataBoundGrid1_CurrentCellControlGotFocus(object sender, ControlEventArgs e)
{
if(e.Control is RichTextBox)
{
RichTextBox rtb = e.Control as RichTextBox;
rtb.AutoWordSelection = false;
}
}