Sum If Question - multiple criteria

[Deleted]

Does a formula exist that can look up and sum sales data based on criteria and by looking for the first instance of a sales and only summing from that point ahead 12 weeks? All the sales data is at week level and spans 27 weeks. 

I am fairly familiar with sum if formulas, but I am stuck on starting to sum from a specific point and only summing a specific number of cells. 

[#2]

@Deleted 

You may use INDEX():INDEX() approach to select a range to sum. Within first INDEX() by MATCH() find position from which to start and add 12 to it within second INDEX(). If you submit small sample file it could be easier to explain on example.