Display countdown timer on simulator for a quiz type application

I am new to blackberry. I want to develop a countdown timer for a quiz type application that displays throughout the application on simulator. I am using 开发者_如何学Gostorm version.'

how to implement it? if anybody answers i will be very thankful to them..

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You can use treads to maintain the timer to force it to redraw the screen after each passing second (use sleep and invalidate functions).