ConditionalF in table too slow. Other solution?

[Weeble]

I have a table where column C are dates and column E are names.
I have a conditional formatting rule that checks for duplicates.. If date and name are duplicate, highlight red. My problem is that since I am using a table I can't specify a range ( excel don't support that yet? ) And right now I am at 12000 rows. When I want to filter it takes forever for excel.
Could I possibly use VBA to to the same thing but in a table range?

For example. VBA
IF Table1 updates
CHECK IF C and F = Duplicates
IF true = Highlight C to F
If false = break

 

[Weeble]

If the table is created with Power Query, then I don't know if there is another way of doing it, as I've never used PQ.

Thank you for the advice. I'll see if I can find a VBA formula that marks duplicates red after a table updates.