PHP function for processing Formidable shortcodes

I'm attempting to create a custom action.  The custom action has a text box setting that allows for entering field shortcodes to get a value entered when the form is submitted.  Does anyone know if there is a built-in PHP function that would take the string set in the text box setting and process any Formidable shortcodes contained inside it?

Example:
Let's say I have a field for chapter name.  The field ID is 100.  Also, I have a field for chapter city and it has a field ID of 200.  I entered [100][200] for the custom action text box setting.  A user submits the form and enters 'chapter1' for field 100 and 'atlanta' for field 200.

In code, I have the custom action value ('[100][200]') in a string variable so I'm wondering if there is a function that would allow me to do something like this:

$result = some_formidable_php_function($custom_action_setting_value);

and $result would then contain the following string: chapter1atlanta

Thanks in advance!