need help for Timer based events

I want to run a timer for a bidding process. The bidding process starts at 9.30am. The bidder will put a quote say 40 .. in say column Q4. The timer starts for 30 minutes. If any bidder quotes within 30 minutes then we will put it in column Q5. Q5 should be < Q4. If it is less than Q4 and greater than zero and before the timer of 30 minutes then the timer is restarted for 30 minutes. If nobody bids within the 30 minutes, then he is the winner and a message "Winner" should be printed in R5. If anybody bids within 30 minutes it will be put in Q6.If Q6 is less than Q4 and Q5 then message "Winner" should be printed in R6. This should go on till 8:00 PM. If nobody bids within 30 minutes then the lowest bidder should be the winner.

can you give me a macro for the above...

Thanks..
Mohak