converting a minute table to a different time period

Hi guys,
I have a huge csv file with date, time, opening price, max price, min price, and closing price. The problem with this file is that some of the minutes are missing in the csv file. I have attached a small sample. I need a vba code that approximates the max/min price for every 30 minutes (as demonstrated by the formula in the example). At the same time i need the opening/closing price as shown by the formula in the example asdf.xlsx.

i need a vba code to do this quickly. alternatively would it be possible to fill the missing minute gaps with minutes repeating the previous row

thanks, I just noticed that the max and min values are wrong. I need the max/min value for 30 minutes meaning the max/min value of approximately 30 cells.

I have reattached the file. I like the way you grouped the data into 1 and 2. The pivot table is confusing. I have highlighted the things i want in green and red. I want the opening value of 17:00 and 17:30 and the closing value of 17:29 and 17:59. I also want the 30 cell max/min of the column that displays max min. In other words, I want the maximum/minimum value of the max/min column from 17:00 to 17:29 and 17:30 to 17:59. You can use my formula on the top right corner as an example. I cant use a macro as I will be applying this on a table with 1 million rows. thankstest.xlsx