Expressions would be the easiest way. Keep a variable for both the minutes, and the seconds. When the seconds are greater than 59, set it to zero, and increment the minutes. Then you need to figure out how to switch the visibility on your object. You can do this by naming your objects the same as the number you need. So 59 would be named 59. You could then change the visibility on the object when the number comes around.
Imagination is more important than knowledge.