I have the following data layout

Col A to E (Row 5) with values say, 10,15,20,25,30

Coll A to E (Row 7) has values say, 15,10,10,30,35

Col A to E (Row 9) returns an "Under" or " " (blank) depending if Row
5 is more or less than Row 7. Thus A9 would show "Under"; D9 would
show "Under" and E9 would show "Under". B & C would show " ".

What I wish t do is add up the difference between A to E Row 5 and Row
7, but ONLY if Row 5 is less than Row 7 i.e. those colmns that show
"Under".

How would I do that via a formula? Hope I am making sense