Hi Marcia,

"CellMouseClick method in DataGridView"
May be you can try something like this part of code:

        private void dgvDataReader_CellMouseClick(object sender, DataGridViewCellMouseEventArgs e)
        {
            if (e.Button == MouseButtons.Right)
                if (e.ColumnIndex != -1 && e.RowIndex != -1)
                {
                    dgvDataReader.ClearSelection();
                    dgvDataReader.CurrentCell = dgvDataReader.Rows[e.RowIndex].Cells[e.ColumnIndex];
                }
        }

HTH