How to detect changed fields only in admin section?

[chamal]

I need to insert some values to custom database table based on the values of changed custom field, if the specific custom field value (in a custom shipping method) had changed.I need to check this in my Observer.php event that I'm firing is 

admin_system_config_changed_section_carriers

is there any possible way to do this ?

[KuafuSoft]

yes, find out the save_after event of your custom modle(usually your_model_name_save_after), and setup an admin observer in config.xml of your custom module

<adminhtml>
        <events>
            <your_model_save_after>
                <observers>
                    <yourObserver>
                        <type>model</type>
                        <class>yourmodule/observer</class>
                        <method>yourMethod</method>
                    </yourObserver>
                </observers>
            </your_model_save_after>
    </events>
</adminhtml>