How do I use last cell w/value with Sum?

[TimB1969]

I want to subtract the value and only that value from my total and then next
month when I enter a value make it recognize that as the last value and
subtract that?

ie Month 1
$10 $5 = $5

Month 2

$10 $5 $3 =$7

so on and so forth

 

[Dave R.]

One way is to use
=INDEX(1:1,MAX(IF(1:1<>"",COLUMN(1:1))))

array entered, to return the rightmost entry in row 1.

 

[Frank Kabel]

Hi
see:
http://www.xldynamic.com/source/xld.LastValue.html