Realign numbers based on change in the month

Hello friends,

In my line of work I do stock forecasting to maintain optimum inventory.

Original sheet shows the forecast quantity for each month for each product
There are times when a product becomes obsolete and its replaced by another product with better specifications. This is called transitioning from one product to another.
Taking example from the attached file in sheet" Original", SKU 533838 was going to transition to 571728 in the Feb-18 until last month based on the stock remaining.
But this month it has changed to Jun-18 again based on current stock remaining.

I want to be able to lookup the month in column H from the sheet "Lookup" and accordingly make changes to the numbers in the original sheet. So the result should look like that in sheet "Result".
Please note I dont want to create a new sheet but amend the numbers in the existing sheet.
There will be numerous product changes and the original sheet has a couple of thousand rows in it so its import to lookup the SKU code within that column.
Can it be done using VBA?

Thank you

Any ideas how this can be tackled?
I am happy to provide any further clarity.

Hi Kev_

Thanks for your response.

But I dont see how its working. The formula is just doing a lookup and putting the month in the column D

What I need is based on the changed month in sheet "Lookup", it should make changes to the numbers that are highlighted in yellow.

Let me explain a bit further.
SKU 533838 is replaced by 571728 in Feb-18. So 533838 has 3 units forecast in Jan and then the forecast moves to SKU 571728.
But as per latest info the replacement will happen in "Jun-18". So SKU 533838 should still show forecast units from Jan - May-18. But from Jun-18 the forecast should move to SKU 571728.

Hope that explains a bit.

Cheers