You need to create a handler for the onkeypress action.
HTML
JS
function handleEnter(inField, e)
{
var charCode;
//Get key code (support for all browsers)
if(e && e.which)
{
charCode = e.which;
}
else if(window.event)
{
e = window.event;
charCode = e.keyCode;
}
if(charCode == 13)
{
//Call your submit function
}
}