Whoever can help

How do you update a cell sum to include a row you have just added to either
the top of your stack or the bottom.

For example if I have the numbers 5,5,5 in cells A3,A4,A5 respectively and
my sum cell is A7 and I add a row either above A43 or below A5 the forumla
won't recognise to include these? Whereas if I added a row between A3,A4 it
would.

I would have thought this may have needed a VB function?

Thanks you in advance for any replies