sumproducts but only last 50 data points

[dmheller]

All,
I have a data set were i do a sum product
=SUMPRODUCT(--ISTEXT(F9:F15249))-COUNTBLANK(F9:F15249)
the column has numbers all down it and sometimes it says null
null is what i am looking for here thats what i am counting.
the data set moves abd currently the last number or null value is at 4989
after that from 4989 to 15249 it is #N/A
I am looking to modify this equation to find the last null or number then count the number of nulls in the last 300 data points. So in this case, number of null from 4989 to 4690. Please let me know if this is do able.
thanks

 

[arthurbr]

The last number ( 0 also being one) can be referenced with INDEX(F:F,MATCH(9.999999e307,F:F,0))
The last 300 would then be referenced as (INDEX(F:F,(MATCH(9.999999e307,F:F,0)-299)):INDEX(F:F,MATCH(9.999999e307,F:F,0)))

 

[dmheller]

Thnaks but i have 2 questions,
With there being a potential 1000 cells below the last "null" or number, will this work.
2nd question, were would this go in the equation so that it counts the nulls in the last 300 good data points?