function CalPay(CalForm) {
    // Formula R = A/((1-(1/(1+i)^n))/i)
    //     '--  R  = nPay
    //     '--  A  = nLoan
    //     '--  n  = 12 * t      (t <--nTerm)
    //     '--  i  = r/100/12    (r <--nRate )
    var nPay=0 ;
    var nCalSq=0 ;
    var nCalAmt= 0 ;
    var nTerm=0 ;
    var nRate=0 ;
    var nLoan=0 ;
    var mas1 = "กรุณาใส่จำนวณวงเิงินกู้" ;
    var mas2 = "จำนวณเดือนผ่อนชำระ= 36 " ;
    var mas3 = "อัตราดอกเบี้ย= 7 %" ; 
   
    nTerm = eval(CalForm.nTerm.value) ;
    nRate = eval(CalForm.nRate.value) ;
    nLoan = eval(CalForm.nLoan.value) ;
    if (nLoan == 0 ) { 
     nLoan = 0;
     alert(mas1) ;
     }
    else {
    
    if (nTerm == 0 ) { 
     nTerm = 36;
     CalForm.nTerm.value = eval(nTerm);
     alert(mas2) ;
     }
    if (nRate == 0 ) { 
     nRate = 7;
     alert(mas3) ;
     CalForm.nRate.value = eval(nRate);
     }     
    n = nTerm  ;
    i = (nRate/100)/12 ;
    nCalSq =(1+i) ;
    nCalAmt=1     ;
    for (var ii=0 ; ii < n  ; ii++) { 
      nCalAmt = nCalAmt * nCalSq ;
     }
    nPay = nLoan/((1-(1/nCalAmt))/i) ;
    nPay = Math.round(nPay,2)        ;
    CalForm.nPay.value = eval(nPay)  ;
   }
   }
   
 // Calculate Credit Amount = Loan Amount
 function CalLoan(CalForm) {
    //   Formula A = R*((1-(1/(1+i)^n))/i)
    //   '--  R  = nPayN
    //   '--  A  = nLoanN
    //   '--  n  = 12 * t      (t <--nTermN)
    //   '--  i  = r/100/12    (r <--nRateN )
    var nPay=0 ;
    var nCalSq=0 ;
    var nCalAmt= 0 ;
    var nTerm=0 ;
    var nRate=0 ;
    var nLoan=0 ;
    var mas1 = "กรุณาใส่ยอดผ่อนชำระต่อเดือน" ;
    var mas2 = "จำนวนเดือนผ่อนชำระ = 36 " ;
    var mas3 = "อัตราดอกเบี้ย = 7 %" ; 
  
    //--    
    nTerm = eval(CalForm.nTermN.value) ;
    nRate = eval(CalForm.nRateN.value) ;
    nPay  = eval(CalForm.nPayN.value) ;
    if (nPay == 0 ) { 
     nPay = 0;
     alert(mas1) }
    else {
    
    if (nTerm == 0 ) { 
     nTerm = 36;
     CalForm.nTermN.value = eval(nTerm);
     alert(mas2) ;
     }
    if (nRate == 0 ) { 
     nRate = 7;
     alert(mas3) ;
     CalForm.nRateN.value = eval(nRate);
     }     
    n = nTerm  ;
    i = (nRate/100)/12 ;
    nCalSq =(1+i) ;
    nCalAmt=1     ;
    for (var ii=0 ; ii < n  ; ii++) { 
      nCalAmt = nCalAmt * nCalSq ;
     }
    nLoan = nPay * ((1-(1/nCalAmt))/i) ;
    nLoan = Math.round(nLoan,2)        ;
    CalForm.nLoanN.value = eval(nLoan)  ;
    
     }
   }

 function CheckNum(CalForm,cStr) {
   var cAdj = ""    ;
   var nFlag= 0     ;
   for (var i=0 ; i< cStr.length; i++) {   
     var ch = cStr.substring(i,i+1) ;
     //-
     if (ch < "0" || ch > "9")  {
       nFlag = 1 ;
       if (cAdj != "" && ch==".") {  nFlag=0 ; }
       //-
       if (nFlag==1) {
         alert("กรุณาป้อนตัวเลขใหม่")  ;
         if (cAdj == "" ) { cAdj="0" }
          CalForm.value= eval(cAdj) ;
          return false   ;
       }   
     }
     //- 
     cAdj = cAdj + ch ;  
     }
     return true ;
   }