Formula to offset a value in excel to a different column?

I am trying to create a formula that offsets an "up-sell" amount 12 periods (columns) in the future.

For background: Each of our customers provides monthly recurring revenue (like a subscription. At the beginning of the model (1/1/18), I have a random number generator from 1-20 that calculates the period in which the customer could be up-sold. As you can see in the photo and the formula that the IF statement looks at the random upsell period and adds in the additional revenue ($100) into that period and periods after that.

I am trying to create the formula so that once the if statement is satisfied (the random period >= the period that the cell is in) it adds the revenue 12 periods later, not in that period itself. For example, Customer ABC's random upsell period is 3, instead of adding that revenue in period 3, I want it to add it in period 15 (12 periods later).

The formula that is currently being used is: =IF($B8>E$5,$C8,$C8+$D$3)

Please see attached image for reference, thank you]1

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