Take the variance of two cells than add back the variance without circular reference

Hi All,

It's more complicated than it sounds.

For work, we put together a COGS estimate each week (which lives in one workbook) and we close our books at month-end. Without having to do any work or paste valuing, I would like to link to the workbook in which we have our actuals and take the variance between the two numbers and add the difference back to the estimate so it actualizes.

So let's say Labor Costs are estimated to be $90,000 for Month 1 and once we actualized it turns out to be $100,000. I would like the for the cell to update with the difference as we close out the month. But as yo ucan imagine, it will cause a circular reference. In it's simplest terms it's

A1 = $90,000 + C1
B1 = $100,000
C1 = A1 - B1

What's the best way to structure this in order to have it automated ? I know I can amend my workbook and have it like this:

A1 = $90,000
B1 = $100,000
C1 = B1 - A1
D1 = A1 + C1

But there are a ton of cells and calculations, I'd hate to restructure the entire workbook.

Please help!