Datagridview rows count based on condition

Hello,
I have changed the backcolor of the rows based on condition, also i have to count the number of rows for the same condition. kindly help me.

this is my code,

            try
            {
                if (e.ColumnIndex == this.dataGridView1.Columns["POST"].Index)
                {
                    string RepVisits = e.Value.ToString();
                    if (RepVisits != null)
                    {
                        if (RepVisits == "M")
                        {
                            this.dataGridView1.Rows[e.RowIndex].DefaultCellStyle.BackColor = Color.LightPink;
                          } 

                        else if (RepVisits == "P")
                        {
                            this.dataGridView1.Rows[e.RowIndex].DefaultCellStyle.BackColor = Color.LightBlue;
                        }

                        else if (RepVisits == "S")
                        {
                            this.dataGridView1.Rows[e.RowIndex].DefaultCellStyle.BackColor = Color.LightGreen;
                        }
                        else if (RepVisits == "F")
                        {
                            this.dataGridView1.Rows[e.RowIndex].DefaultCellStyle.BackColor = Color.LightCyan;
                        }
                        else
                        {
                            this.dataGridView1.Rows[e.RowIndex].DefaultCellStyle.BackColor = Color.White;
                        }
                    }
                }
            }
            catch
            {
             }