This is untested, but, to change the value from '500' to 'random' on the form:
Code:
<input type="hidden" value="random" name="amount" />
Module PHP Code will now check that the value is 'random':
PHP Code:
if((isset($_POST['amount']) && !empty($_POST['amount'])) && $_POST['amount'] == "random") {
$amount = rand(500,2000);
$mysidia->user->changecash($amount);
}
Should work and be plenty secure. ^^