function calculate() {
  f = document.forms.calculator;
  f.gross.value = f.gross.value.replace(/[^0-9]/g,"");
  f.net.value = f.gross.value - parseInt(f.gross.value/20);
  return false;
}

document.write('<style>');
document.write('.text {font-family: arial, sans-serif; font-size: 10pt; margin-left: 5; margin-right: 5; margin-top: 5; margin-bottom: 5; color: #f0f0f0; font-weight: bold;}');
document.write('.cal_table {border: #ff0000 3px solid;}');
document.write('.cal_innertable {border-collapse:collapse;}');
document.write('.cal_td {border-top: #c2e0d6 3px solid; border-bottom: #c2e0d6 3px solid; background-color: #1b2b8a;}');
document.write('.button {background-color: #eeeeee; font: arial; font-weight: bold; color: #1b2b8a; font-size: 9pt; margin-left: 5; margin-right: 5;}');
document.write('</style>');

document.write('<table align=center class=cal_table cellpadding=0 cellspacing=0><tr><td>');
document.write('<form name=calculator onSubmit="return calculate()">');
document.write('<table align=center class=cal_innertable><tr>');
document.write('<td class=cal_td><p class=text>Gross Commission</p></td>');
document.write('<td class=cal_td><input type=text name=gross size=4 style="text-align:right; padding-right: 3px;"></td>');
document.write('<td class=cal_td><input type=submit value=">> Calculate >>" class=button style="width:100px;"></td>');
document.write('<td class=cal_td><input type=text name=net size=4 style="text-align:right; padding-right: 3px;"></td>');
document.write('<td class=cal_td><p class=text>Agent Net Amount</p></td>');
document.write('</tr></table></td></form></tr></table>');