Disable GridView TextBox typing if TextBox outside is empty using jQuery in ASP.Net

I have set condition that when ever txttotalday is empty then gridview row absent get empty if some value input give message

below code

        protected void OnCalculate(object sender, EventArgs e)
        {
            TextBox absent = sender as TextBox;
            GridViewRow row = absent.NamingContainer as GridViewRow;
            Label present = row.FindControl("txtpresent") as Label;
            Label gsalary = row.FindControl("EMP_Salary") as Label;
            Label lbLoan = row.FindControl("Loan") as Label;
            Label lbAdvance = row.FindControl("Advance") as Label;
            Label lbMobile = row.FindControl("Mobile") as Label;
            Label lbConveyance = row.FindControl("Conveyance") as Label;
           
            Label lbMedical = row.FindControl("Medical") as Label;
            Label lbfood = row.FindControl("Food") as Label;
            Label nsalary = row.FindControl("txtsalary") as Label;
   
            Label lbOT = row.FindControl("emp_OT") as Label;
            TextBox txthours = row.FindControl("txthour") as TextBox;
            Label lbOT_Amount = row.FindControl("lbOT_Amount") as Label;
            Calculate(txttotalday, present, absent, gsalary, nsalary, lbAdvance, lbLoan,lbMobile, lbMedical, lbfood, lbConveyance, lbOT, txthours, lbOT_Amount);

            DataTable dt = (DataTable)ViewState["dt"];
            dt.Rows[row.RowIndex]["txtpresent"] = Convert.ToDecimal(present.Text.Trim());
            dt.Rows[row.RowIndex]["txtabsent"] = Convert.ToDecimal(absent.Text.Trim());
            dt.Rows[row.RowIndex]["txtsalary"] = nsalary.Text.Trim();
            dt.Rows[row.RowIndex]["Food"] = lbfood.Text.Trim();
         //   dt.Rows[row.RowIndex]["lballowance"] = allowance.Text.Trim();
            dt.Rows[row.RowIndex]["emp_OT"] = Convert.ToDecimal(lbOT.Text.Trim());
            dt.Rows[row.RowIndex]["txthour"] = Convert.ToDecimal(txthours.Text.Trim());
            dt.Rows[row.RowIndex]["lbOT_Amount"] = lbOT_Amount.Text.Trim();




            ViewState["dt"] = dt;

        }
        private void Calculate(TextBox total, Label present, TextBox absent, Label gsalary, Label nsalary, Label lbAdvance, Label lbLoan,Label lbMobile,Label lbMedical,Label lbfood, Label lbConveyance, Label lbOT, TextBox txthours, Label lbOT_Amount)
        {
            if (txttotalday.Text == "" )

            {
                 
                Response.Write("<script language='javascript'>alert('please input total days');</script>");
                
            }

            else
            {
                lbOT_Amount.Text = (Convert.ToDecimal(txthours.Text) * Convert.ToDecimal(lbOT.Text)).ToString();

                present.Text = (Convert.ToDecimal(txttotalday.Text) - Convert.ToDecimal(absent.Text)).ToString();



                nsalary.Text = ((Convert.ToDecimal(gsalary.Text) / Convert.ToDecimal(total.Text) * Convert.ToDecimal(present.Text) + Convert.ToDecimal(lbOT_Amount.Text) + Convert.ToDecimal(lbMobile.Text) + Convert.ToDecimal(lbMedical.Text) + Convert.ToDecimal(lbfood.Text) + Convert.ToDecimal(lbConveyance.Text) - Convert.ToDecimal(lbLoan.Text) - Convert.ToDecimal(lbAdvance.Text)).ToString());

                nsalary.Text = Math.Round(double.Parse(nsalary.Text), 0).ToString();

            }
        }