90TH Percentile

Hi,
I need to find out the 90th percentile of a set of times but with conditions. I have rows with data that need to be considered in the percentile. The first column has the incident numbers (there are duplicate values because there are different staff showing up at different times for the same incident). The second column has the times the staff showed up and the third column has the amount of staff that showed up each time. I only want to consider the times in the percentile that incorporate the first 12 staff, this may just be the first 3 times if 4 staff show up each time. However I am not sure how to create the formula that will find the times of the first 12 staff members and ignore the other times of any staff over 12. I need a formula that will copy down because I have data for about 300 different incidents to look at. Hopefully there is a way to do this.

Incident Response times # of staff
HF16-2 0:11:36 4
HF16-2 0:05:48 4
HF16-2 0:06:56 2
HF16-2 0:03:20 4
HF16-2 0:02:19 4
HF16-2 0:08:40 1
HF16-3 0:12:05 4
HF16-3 0:02:03 4
HF16-3 0:08:45 1
HF16-3 0:03:54 4
HF16-3 0:07:40 2
HF16-3 0:05:11 4
HF16-4 0:58:26 0
HF16-4 0:05:40 0
HF16-4 0:06:04 0
HF16-5 0:06:17 2
HF16-5 0:04:50 2

Thank you.

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Goodness gracious, I apologize if my title was non compliant.