function disc_factor(frm_numb){ var a; a=eval(document.forms[frm_numb].l_amount.value); b=eval(document.forms[frm_numb].term_years.value)*12; c=eval(document.forms[frm_numb].an_int_rate.value)/(12*100); coef=((Math.pow(1+c,b)-1)/(Math.pow(1+c,b)*c)); return coef; } function over_calc(){ resul_win=window.open("",""); resul_win.document.write("Mortgage Overpayment Results

Loan Amount: "+document.f3.l_amount.value+"
Term:"+document.f3.term_years.value+" years
at Annual Interest Rate: "+document.f3.an_int_rate.value+"%
Overpayment £"+document.f3.over_pay.value+" /mo.
"); factor=disc_factor(0);// "0" data from form #1 corr_f=0;//correction factor outstand=document.f3.l_amount.value; m_princ_paid=0; tot_inter_paid=0; m_inter_rate=eval(document.f3.an_int_rate.value)/(12*100); over_pmnt=eval(document.f3.over_pay.value); m_paiment=outstand/factor+over_pmnt; term_mon=eval(document.f3.term_years.value)*12; m_paiment=Math.floor(m_paiment*100)/100; resul_win.document.write(" You will pay monthly : £"+m_paiment+"
£"+eval(m_paiment-over_pmnt)+" req. payment + £"+over_pmnt+" overpayment

"); // resul_win.document.write(""); rez=0; for(i=1;i<=term_mon;i++){ m_inter_paid=outstand*m_inter_rate; tot_inter_paid+=m_inter_paid; m_princ_paid=m_paiment-m_inter_paid; outstand-=m_princ_paid; if(outstand<0 || term_mon==i){//last period check m_princ_paid=m_princ_paid+outstand; corr_f=outstand; outstand=0; } k=Math.floor(i/12); if(i/12==k){ year_pr=""+Math.floor(k)+""; } else year_pr="
"; // resul_win.document.write(""); if(outstand<=0||term_mon==i) {rez=i;i=term_mon+1;} } xx=(m_paiment-over_pmnt)*term_mon-document.f3.l_amount.value-tot_inter_paid+corr_f; xx=Math.round(xx*100)/100; rez=term_mon-rez; last_p=Math.round(m_princ_paid*100)/100+Math.round(m_inter_paid*100)/100; resul_win.document.write("
You will pay the mortgage "+rez+" months earlier
and will pay £"+xx+" less for interest "); resul_win.document.write("

*"+eval(term_mon-rez-1)+" payments of £"+m_paiment+" and 1 last payment of £"+Math.round(last_p*100)/100+"
Amortisation Schedule
YearMonthPrincipal PaidInterest PaidOutstanding Balance
"+year_pr+""+i+""+Math.round(m_princ_paid*100)/100+""+Math.round(m_inter_paid*100)/100+""+Math.round(outstand*100)/100+"
"); resul_win.document.write("
"); ///////// return true; }