Conditional Formatting

if you select the range - it will also apply to BC5

for 2007, 2010 , 2013 , 2016 , 2019 or 365 Subscription excel version
Conditional Formatting

Highlight applicable range >>
BC4:BC5 - Change, reduce or extend the rows to meet your data range of rows

Home Tab >> Styles >> Conditional Formatting
New Rule >> Use a formula to determine which cells to format
Edit the Rule Description: Format values where this formula is true:
=BC4>9

Format [Number, Font, Border, Fill]
choose the format you would like to apply when the condition is true
OK >> OK

otherwise

A sample sheet would help here

The forum does allow for spreadsheets to be uploaded direct to the forum -

Please see the Yellow Banner at the top of the page explaining how to attach a sample spreadsheet

A good sample workbook has just 10-20 rows of representative data that has been desensitised. It also has expected results mocked up, relevant cells highlighted and a few explanatory notes.

Here are the instructions, found at the top of the page again

Post a small Excel sheet (not a picture) showing realistic & representative sample data WITHOUT confidential information (10-20 rows, not thousands...) and some manually calculated results. For a new thread (1st post), scroll to Manage Attachments, otherwise scroll down to GO ADVANCED, click, and then scroll down to MANAGE ATTACHMENTS and click again. Now follow the instructions at the top of that screen.

so you dont need
=IF(BD4>9,"TRUE","FALSE")
just
=BD4>9

and you can apply to a range
at the moment
it applies to D4 - F4
if you want to use the same cell - then the cell needs to be fixed
=$BD4>9
Now c4,d4,ef,f4 will still check BD4

otherwise i'm not sure why you are copying the conditional formatting