How To plus And Show Value ?

Question

 

 

 

private void BILLNO_SelectedIndexChanged(object sender, EventArgs e)

{

}

private void PERVIOUS_TextChanged(object sender, EventArgs e)

{

}

private void CHARGESAMOUNT_TextChanged(object sender, EventArgs e)

{

}

private void TOTAL_TextChanged(object sender, EventArgs e)

{

}

 

Display and SHow Pluse Value