Custom Fields values before form submit

Is there an easy way to grab values from text boxes in an Advanced Custom Fields form and use them in functions.php. I am trying to grab a city and address value to calculate googlemap coordinates in functions.php when the user hits publish. I tried testing get_field() but it seems to only work after the info has been written to the database.

Basically I want to grab these values do a calculation and enter new meta values in the database when the user hits submit. But I can only seem to grab the field values from the database and not the form itself.