function Vorhalt(){
     v0 = parseFloat(document.D.v0.value);
     v100 = parseFloat(document.D.v100.value);
     troll = parseFloat(document.D.troll.value);
     flucht = parseFloat(document.D.flucht.value);

     var v20d = v0 + 20/100 * (v100 - v0);
     var v40d = v0 + 40/100 * (v100 - v0);
     var v60d = v0 + 60/100 * (v100 - v0);
     var v80d = v0 + 80/100 * (v100 - v0);
     var v100d = v0+ 100/100 * (v100 - v0);

     var  t20 = 20 / v20d * troll; var  f20 = 20 / v20d * flucht;
     var  t40 = 40 / v40d * troll; var  f40 = 40 / v40d * flucht;
     var  t60 = 60 / v60d * troll; var  f60 = 60 / v60d * flucht;
     var  t80 = 80 / v80d * troll; var  f80 = 80 / v80d * flucht;
     var t100 = 100 /v100d* troll; var  f100 = 100 / v100d * flucht;

     document.D.vt20.value = t20.toFixed(2);
     document.D.vf20.value = f20.toFixed(2);
     document.D.vt40.value = t40.toFixed(2);
     document.D.vf40.value = f40.toFixed(2);
     document.D.vt60.value = t60.toFixed(2);
     document.D.vf60.value = f60.toFixed(2);
     document.D.vt80.value = t80.toFixed(2);
     document.D.vf80.value = f80.toFixed(2);
     document.D.vt100.value = t100.toFixed(2);
     document.D.vf100.value = f100.toFixed(2);
     alert("Bei Flucht halte auf 100 m schon "+f100.toFixed(2)+" m vor!");
	}