2个form比如
form1 和 form2  把事件写在onsubmit里面就可以
例子
<form id=form1 onsubmit="alert('form1 submit')">
<input id="b1" type=submit value="button1">
</form>
<form id=form2 onsubmit="alert('form2 submit')">
<input id="b2" type=submit value="button2">
</form>