How to insert into Database table when months changed ?

float PayMomth,PayTotal;

DateTime PayDate;

private void button4_Click(object sender, EventArgs e)

PayTotal = float.Parse(textBox2.Text);

while(PayTotal>0)

if(PayTotal>=100)

wor.addbill(PayDate, Convert.ToInt32(comboBox1.SelectedValue),PayTotal, Convert.ToDateTime(dateTimePicker2.Text));