Insert user name into a record

In Events - Global Pages - Login Page - After Successful Login
Put in your session like this:
$_SESSION["UserName"] = $data["username"];

Then in your Fields - Whatever table for your Username field click on Properties Box Pick Readonly Then in the Default value use $_SESSION["UserName"] Or click on the ... and in drop down at the top pick Username and it marks it for you. Same for add and edit.