Display the last value of an array
 

How can I display in a cell the last value of an array that is continuously
being updated? For example, I have the array A1:A8 with the following values
A1 5
A2 10
A3 16
A4 20
A5
A6
A7
A8
I would like to display the last value I have. In this case the last value
is "20". But when "A5" is filled in with "30" then I would like that it would
appear "30".
Thank you!