How to specify multiple submit handlers for multiple forms
You can specify a submit handler for each of your forms. Examples:

Override default handler with custom handler (new array):

$form['#submit'] = array('data_retrieval_form_submit');


Run custom handler after default (append to array):

$form['#submit'][] = 'data_retrieval_form_submit';


Run custom handler before default (prepend array):

array_unshift($form['#submit'], 'data_retrieval_form_submit');


You can add it to the $form array in a custom form builder function, or alter an existing form via hook_form_alter.