Conditional Formatting/COUNTIF help with multiple criteria

Let me start this off by saying I am not a professional, and am so uneducated that I don't even know that I have the right search terms (because I couldn't find an answer, I did try) or the best formula for this solution.

Okay, so. What I have is a multiple page spreadsheet; page one is "Active" (all clients; unique ID number, first and last names, and a column for each type of report), page 2 is "Pending," (clients ID#, name, and whichever specific provider a request has been sent out, and the date out) and page 3 is "Received" (all of the received reports from page 2, with added received and effective dates).

I have a number of conditional formatting rules in place, including one to make sure that reports are not duplicated using a helper column and COUNTIF on pages 2 and 3, and another COUNTIF to highlight the first names of clients on page 1 that have an entry on page 2 (using the unique ID# but highlighting the name cell).

What I'm trying to do - using similar logic to the second rule mentioned above - is create a rule where I can make the second name be highlighted on page 1 if there is an entry on page 3 AFTER a certain date, in a cell that I can change as I update the Active page by adding the information in the Received page.

I'm close, I think! I tried some other functions but ended up using a helper column (might as well) managed to figure out

=COUNTIF(Received!$L$2:$L$1078,$C2&$P$8)>0

Where P8 is the last updated date, L is my helper column (ID and date).... but I can only make it EQUAL to P8, not after. That works great, and I guess I could do it one day at a time, but that isn't optimal.

I know I am close, but I just can't figure out what I can do. I tried adding in a greater than sign but it kept giving me errors and damned it, I am stymied, and I JUST KNOW there is a solution somehow.