Count number of values, until the sum of underlying values meets condition

I have the following problem.

I have 1,000 units of stock in inventory and I need to know when I'm running out of stock.

Over the next 12 weeks I'm forecasting to sell the following number of units (assuming I had unlimited stock):

Week 1: 50
Week 2: 50
Week 3: 50
Week 4: 50
Week 5: 300
Week 6: 300
Week 7: 300
Week 8: 400
Week 9: 300
Week 10: 200
Week 11: 100
Week 12: 50

I'd like to get a formula that basically sums up the above values in an array, and stops when the sum exceeds the initial 1,000. then the formula spits out the count value, i.e. how many weeks where added up before the value exceeded 1,000. This would then tell me that I'm running out in 7 weeks from today (i.e. adding up the first 7 values gets you number bigger than 7).

Not sure if this is possible.

Unfortunately I cannot do a helper column to calculate the cumulative value.

Would be HIGHLY appreciated!

Thanks for the quick response. my data is actually organized horizontally, so values are in A1, B1, C1 etc.

how would the formula have to be amended to work in that format?

Thanks a lot in advance!