I'm not clear what you mean by "represents". The logger records every minute, but you only want the data from every fifth or fifteenth minute? Or do you want a running average of those measurements based on those intervals?

The former probably requires a helper column which should be fairly easy. 15 minutes in Excel is equal to 15/(24*60). You could set up a helper to only identify those rows where the mod() of the time with that ratio is zero or something like that.

For the latter, you can group and average with a pivot, but only by minutes, hours, days, etc. To do so by 5 minutes or 15 minutes would require a helper column which should be even easier.

Making it robust to manage the intervals to satisfy your regulations is mere window dressing. Should be pretty easy.

Thank you for the assistance

here is what I have come up with ...what do you think

1. Copy data to a new sheet and remove unneeded columns
2. Create a helper column and insert this code in the first cell of the helper column.
3. =(Mod(Minute(cell#), xx)) where "xx" = the number of minutes to filter by eg.. 5 or 10 or ….
4. Copy the formula down to the last row
5. Select all of the data rows
6. Select filter from the data menu
7. From the drop down arrows on the helper column select number filters > does not equal
8. In the box next to the "does not equal" enter “0” and select OK
9. Right click in the middle of the data and select delete rows.
10. You will now be left with only the rows containing the minutes selected.