Solution:
Are you trying to do something like this ?
<?php
function myfunc()
{
$a=2;
return $a;
}
function wplogincontrol(){
$val = myfunc();
if ($val=="2")
{
header"Location: http://www.google.com");
exit;
}
}
add_action('login_head', 'wplogincontrol');
?>