I want to have table with just 3 records (rows) and i want work it as FIFO

if i add 100
it will go on 1st row
and then if i add 200
it will go in 1st row and 100 should go in 2nd row
and then if i add 300
it will go in 1st row and 200 will go in 2nd row and 100 will go in 3rd row

and when i would add 400 then it would go in 1st row with 300 in 2nd row and 200 in 3rd row but 100 should be deleted.

little complex

But i am finding here an easy way to do it.
Thank You.