Searching column "B" then report the value in the adjacent cell in column "A"

[Kindlysinful]

I have two columns of data, A and B
What I do is find the max number in column B, report that value in C3. Easy enough with =MAX(b2:b5000).
What I need to do next is find what 80% of that value is then search “B” for a number equal to or just above that 80% value. Then reference the adjacent cell in “A” and report the value in column "A" in C4.

 

[aaronbens]

If you can add a column of data then the following should work:
If your data set is A2:B5000, as noted C3 = MAX(B2:B5000)
In cell D2 you can add the formula =IF(B2-($C$3*0.8)<0,"",B2-($C$3*0.8)) can fill down to D5000.
C4 =INDEX(A2:A5000,MATCH(MIN(D2:D5000),D2:D5000,0))

 

[Kindlysinful]

Not having much luck. It is returning a -1.

 

[aaronbens]

Can you post a sample of the dataset and what the output is based on the set you provide?

 

[Kindlysinful]

So sorry for the extended delayed response, I was called out of the country for work. I will try and post an example but I was not seeing any borders.

 

[Kindlysinful]

Time (ms)	Pressure
-0.030	6.713867
-0.025	6.103516		685.66781	Max Psi
-0.020	5.493164			Time to 80% Peak
-0.015	6.103516
-0.010	5.493164
-0.005	5.493164
0.000	5.493164
0.005	6.103516
0.010	6.103516
0.015	5.493164
0.020	6.103516
0.025	5.493164
0.030	4.882812
0.035	6.713867
0.040	6.713867
0.045	4.882812
0.050	6.103516
0.055	5.493164
0.060	6.713867
0.065	6.103516
0.070	6.103516
0.075	7.324219
0.080	6.103516
0.085	5.493164
0.090	6.103516
0.095	6.103516
0.100	6.103516
0.105	7.324219
0.110	6.103516
0.115	4.882812
0.120	5.493164
0.125	7.324219
0.130	5.493164
0.135	6.713867
0.140	6.713867
0.145	6.103516
0.150	6.103516
0.155	6.103516
0.160	5.493164
0.165	5.493164
0.170	5.493164
0.175	6.103516
0.180	5.493164
0.185	5.493164
0.190	6.103516
0.195	6.103516
0.200	6.103516
0.205	6.713867
0.210	6.103516
0.215	6.103516
0.220	5.493164
0.225	5.493164
0.230	5.493164
0.235	5.493164
0.240	6.103516
0.245	6.103516
0.250	4.882812
0.255	5.493164
0.260	5.493164
0.265	5.493164
0.270	6.103516
0.275	4.272461
0.280	5.493164
0.285	6.103516
0.290	6.103516
0.295	4.882812
0.300	6.103516
0.305	6.103516
0.310	6.103516
0.315	6.103516
0.320	6.103516
0.325	6.713867
0.330	10.0001
0.335	12.3242
0.340	16.9087
0.345	100.7653
0.350	104.2196
0.355	131.90761
0.360	159.59562
0.365	187.28363
0.370	214.97164
0.375	242.65965
0.380	270.34766
0.385	298.03567
0.390	325.72368
0.395	353.41169
0.400	381.0997
0.405	408.78771
0.410	436.47572
0.415	464.16373
0.420	491.85174
0.425	519.53975
0.430	547.22776
0.435	574.91577
0.440	602.60378
0.445	630.29179
0.450	657.9798
0.455	685.66781

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