How to make custom the options.php correctly

Hi guys, im building a plugin, i have an administration page of this plugin in the settings of my wordpress, in that page i have a form like this

<form name="frm1" action="options.php" method="POST">

 <!--....... all the form ....... -->
 <input type="submit" value="Save settings" class="button-primary />"
</form>

Well, in the action=”” of the form i call the file options.php in orther to show the message “settings saved” when the submit button is pressed.

I need to catch some values of this form, i can do that just creating another file and change the action=”” of the form and get the values for example like this

$_POST['checkboxValue-forExample'];

But how can i use the options.php for show the “settings saved” message and my custom action at the same time?

Do i have to copy and paste all the options.php to another file, and then modify it for catch the values that i need????, i can do that… but i think its not a the correct way.

Thanks for answer.