Vlookup rounding with dates

[Prevost]

Hi There. I have a table that contains the date in DD/MM/YYYY HH:MM:SS format and I want to use VLOOKUP to find the average temperature for the corresponding date in another worksheet. The dates in the weather data worksheet are in the same format. The average temperatures are given hourly, but I need those temperatures for 5 minute interval data (so the average temperature for 1:00PM will be the average temperature for 1:00, 1:05, 1:10,...etc). It works almost perfectly but VLOOKUP puts the average temperature for 12:00 in the space that it should be 1:00, but then correctly uses 1:00 for 1:05. I am using an approximate match, so that could have something to do with it. I have tried using ROUND, ROUNDUP and ROUNDDOWN but they all seem to misread the exact matches while providing what I want for the other temperatures. Anyone have any suggestions?
Thanks!

 

[GerryZ]

hello can you post a sample with few rows and few columns with the expected outcome?

 

[Prevost]

Sure thing. The selected cell in the first picture should read -8.8 (from the second picture) but instead reads -10.6...the 13:00 value is still using the 12:00 value.