hi. I've attached sample workbook(with sensitive data removed).

i have a large sheet (300000 rows) of data. the data has been collected in 10min increments over a year. calculations where carried out to define each 'time' as either stable, neutral, or unstable.

I really need data in the second sheet to 'reference' sheet1 and determine itself as either stable,neutral or unstable. it would do this by its own time and date and matching it to sheet one.

I don't know how to do this! if anyone could point me in right direction I'd be forever grateful.

I'm a 4th year engineering student from scotland, and really need this last piece of the puzzle to complete my data analysis.

thank you!!