private void button4_Click(object sender, EventArgs e)
{
if (txttenure.Text == "1")
{
b = Convert.ToInt32(txtijarahamount.Text);
for (int j = 1; j <= 12; j++)
{
int newRowIndex = dataGridView1.Rows.Add();
int z = 12;
markup = double.Parse(txtmarkup.Text);
Double a = (b / 100) * 80;
prfrate = (markup + 3.00) / 100.00;
bnkprf = (a * prfrate * 31.00) / 365.00;
rental = (a + bnkprf + 30000) / z;
z--;
string r = Convert.ToString(rental);
dataGridView1.Rows[newRowIndex].Cells["Amount"].Value = r.ToString();
a = a - Convert.ToDouble(dataGridView1.Rows[newRowIndex].Cells["Amount"].Value);
r = Convert.ToString(rental);
dataGridView1.Rows[newRowIndex].Cells["Date"].Value = dateTimePicker1.Value.Date.AddMonths(j).ToString();
dataGridView1.Rows[newRowIndex].Cells["ijarah_id"].Value = txtijarahid.Text;
}