[kh99]

If the field is already created and you have php code that's setting the other fields, you can set the menu options of your Main Player field like this:

$players = array();
$players[1] = "Rogue";
$players[2] = "Mage";
// etc

$menuid = ID; // Change ID to profile field id of menu
global $vbulletin;
$vbulletin->db->query_write("UPDATE " . TABLE_PREFIX . "profilefield
                              SET data = '" . $vbulletin->db->escape_string(serialize($players)) . "' 
                              WHERE profilefieldid = $menuid");

Note that members won't have any value for this field until they set it themselves, unless you also update the userfield table.