Finding the Difference Starting with Zero Dollars

[The_Game]

I'm trying to find the difference of two arrays and have it tell me the difference starting with zero and counting up. I've got two columns, Sub Total (estimated cost) and the Actual total (cost at the time of sale). The Actual hasn't been set up because we haven't purchased anything yet, hence the example. Because these values can change once items are purchase, I want to track if parts cost more or less and show me a total difference that sum up from zero, instead of counting them down from $74K. This way I can reference how much I've got to scrape off the top to allocate elsewhere as items are purchased. Is there a way to calculate the difference from zero and work my way up to $70K (assuming everything I purchase is worth $1)?

Tables aren't working on this computer, so bear with me.


Subtotal Example Actual Total Actual Total Difference
$100.12 $112.13 ... -12.01
$1122.30 $1000.00 ... +122.30
... ...
... ...
Totaling: $74,135.11 Total Difference: +110.29