you aren't going to be able to accomplish this with the page submitting. the page needs to submit to reset the session valriable values, and regenerate the map javasacript based on those values.
I would set up Pro Maps to get the latitude and longitude from the session variables.
use the ajax function to populate hidden form elements with the new latitude and longitude, when the page submits, set the Session Variables to get their values from the hidden form elements.