CountDownNumber Help

This is a game which comes in a daily program in BBC Channel 4 in United Kingdom. I just took the idea and tried to implement the Count-Down Number Game.
How to Play : There are 6 "small" and 6 "Large" buttons. These buttons will give you a random number. If you click the small button then you will get a number in the range of 1-10, and when you will click the large button then you will get a number 25 or 50 or 75 or 100. You can choose any 6 numbers all in total. Those numbers will be displayed at the text fields. Now you can click the button labeled "Random Number" which will give you a random number in between 1-999. Now its your job to achive the Random Number by manipulating one or more number from the 6 small or large numbers that you had choosen before. You can use a number only once. You can use any of these mathematical operations : + , - , * and / . ALL THE BEST.