<script language="javascript"> function calculate(){
document.form.action="oblicz.php";
document.form.target="new";
}
function wykres(){
document.form.action="wykres.php";
document.form.target="";
}
a potem:
<form method="post" name="form"> ...
<input type="submit" name="Wyslij" value="Oblicz" onClick="calculate();" /> ...
<input type="submit" name="zamow" value="Zamow" onClick="wykres();"/>
chyba o to chodziło...