<script type="text/javascript">
<!--
function test(){
var vorname = document.blub.vor.value;
var nachname = document.blub.nach.value;
var vorname2 = document.blub.vor2.value;
var variable4 = nachname+" "+vorname+" "+vorname2;
return document.blub.gesamt.value=variable4;
}
-->
</script>
<form name="blub" action="">
<input type="text" onkeyup="javascript:test();" name="vor" value="">

<input type="text" onkeyup="javascript:test();" name="nach" value="">

<input type="text" onkeyup="javascript:test();" name="vor2" value="">

<input type="text" name="gesamt">
</form>

function name()
{
	var nachname  = document.FORMULAR.FAMNAME.value;
	var vorname_1 = document.FORMULAR.VORNAME.value;
	var vorname_2 = document.FORMULAR.VORNAME2.value;

	var name = nachname+" "+vorname_1+" "+vorname_2;
					
	return document.FORMULAR.NAME_V.value=name;

}

<form name="FORMULAR" action="inhalt.php" target="_self" method="post">
<td><input type="text" name="NAME_V" size="35" value="" readonly="readonly"></td>
<td><input type="text" name="FAMNAME" size="35" maxlength="35" onkeyup="name()"></td>
<td><input type="text" name="VORNAME" size="20" maxlength="20" onkeyup="name()"></td>
<td><input type="text" name="VORNAME2" size="20" maxlength="20" onkeyup="name()"></td>