Find the 1st value to cross a specific threshold value

I need a query to get the first value greater than a specific threshold valueLoadTemp1 LoadTemp2 LoadTemp3 LoadTemp4 TimeStamp300 200 100 320 12-10-2013 13:30:29100 250 113 340 12-10-2013 14:20:12114 339 209 345 12-10-2013 14:45:01I need to get the first value >= 340 thresholdI need to make a Benchmark on when the first LoadTemp crosses Threshold of 340 and capture the time.Please help.