Just to explain what KLS did with the platinum check there (in case you don't have any programming background).
Code:
if($platinum > 0 && $platinum <= 250000 && ($platinum % 25000) == 0)
returns true when the platinum amount is greater than 0, but less than 250000 and when divided by 25000 has no remainder (so any amount between 25000 and 250000 in intervals of 25000).