I am not an expert, just want to give my ideas
.
U can have one more field in Table, Like Last rertieved time of a the question, then U jus write a query to retrieve the question which has the least time.... When ever u retrieve the question, Update the Last retrieved time field in the table.
How aften means.... That last retrieved time field in the table decide automatically, based on questions answered..
I am jus a begginner, Hope this idea works
Regards
Naresh