Paper Trail ("first usage" timestamp for first login (following registration) required)

Hello,
In order to comply with some jurisdictions, I must have a clear "paper trail".

(1) Presenters register at presenters_registration.php which is simply a styled SecurityAssist page where I collect "Basic Login Details" (first, last, username, password)

(2) Since I need further info and a timestamp, then upon success for above, they go to a fuller presenter_switchboard_data_update_initial.php where I collect fuller details addresses, etc. Upon hitting submit I assign them a code based on their name (would be RBO1 for you); and also insert a timestamp into the database to show when this was done.

(3) Above timestamp not really satisfactory, because it is recording when they submitted data, and not when they first logged in to use fuller site.

(4) And now, of course, upon submitting information, and when I send them back to the login page to do a first login for which I can collect a REAL timestamp, security assist is marking them as "already logged in". So these people are not having their sessions cleared and being forced to login all over again, and so that for these first login people, I can then overwrite the above timestamp in (2) for a REAL first timestamp of when they actually logged in for the first time to use the site.

I have tried a variety of strategies, such as creating a dedicated login page JUST for these users, rather than a bunch of if-then statements in the more usual login page, but nothing seems to be working.

Essentially, I need to devise a specific code for every presenter (so a Roy Boulton would now get RBO2); and also log their first entry into the site after having given their information, and to demonstrate (again, required in some legal jurisdictions) their "true consent" by actually using the site.

Could you please advise if I am using the right method? Or else what I need to do to the login page so after people have submitted their data in my above presenter_switchboard_data_update_initial.php page they are forced to login and I can collect the timestamp I require.

I hope I have stated this clearly!!!!

I attach the two pages concerned

Thank you very much,
KAB