Sorry Mike,

I'm having trouble deconstructing your request. Let me break it down the way I comprehend and please adjust accordingly.
Data to focus
1)Same Stock Symbol logged.
2)(K)Open Date ex: 3/2/21
3)(AC)Close Date ex: 3/31/21

Highlight stock because open within 31 days to close

1)Same Stock Symbol logged.
2)(K)Open Date ex: 2/2/21
3)(AC)Close Date ex: 3/31/21

DO NOT Highlight stock because open is OVER 31 days to close


If I read that right please try:
=SUMPRODUCT(($F$9:$F$1000=F9),(($AC$9:$AC$1000)>=K9 - 31))>1