There are several ways to go about something like this. You can actually have more than one submit button per form. Give all the buttons the same name, but have differnet values for each.
<input type="submit" name="Command" value="Save"><br>
<input type="submit" name="Command" value="AddRow"><br>
In your PHP, look for the value of code like this:
$command = $_GET['Command'];
if("Save" == $command)
elseif("AddRow" == $command)
//Add a Row
Depending on which command you just processed you can display different buttons. Does this help?