Function including a variable range

I have a spreadsheet that keeps track of stock. I have an attention status that tells me if there is overstock (refers to a cell with a fixed amount), attention lets me know if stock is less than lead time(lead time is the total time to restock that item) and ok if neither criteria are meant. Each product has a different lead time. If you look at my attached spread sheet I would like my current status function to refer to that products lead time plus 2 weeks. For example if we are in week 50 and the lead time is 12 weeks then the function would refer to the stock count in week 10. However I would like to add two weeks on to that for a margin of safety. So for the above example I would like my function to refer to week 12. Please let me know if there is a function that will incorporate current week and lead time as a variable rage in my current function.Status Function.xlsx

Results should be equal to what is in week 13. The 13 week lead time means I should be looking in week 11 since it is 13 weeks from week 50, however I want to add 2 weeks as a safety net so this results in my status function looking at week 13. My lead time is a variable amount. Thanks.

1: Overstock
2: Overstock
3: Attention