You can use the classes NumberField and Arrow_Button of this demo in any scenario. Description of the methods are in the classes. I hope this demo can help you in your scenarios.
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A new version of this scenario was uploaded on Sun Mar 03 14:13:19 UTC 2013
Improved the reaction of the numberfields for the user input.
Also fixed a bug concerning the edge values.
A new version of this scenario was uploaded on Sat Mar 09 13:26:40 UTC 2013
Improved the arrow button funktion.