Can't you reference that workbook in a formula in a spare cell and use that cell in Conditional Formatting?
Conditional Formatting -> New Rule -> Use a Formula to Determine which Cells to Format
Format values where this formula is true:
=SheetName!L362="2nd Airing"
Applies to:
=D25
Format:
Red
Yea, as far as I'm aware there isn't a way to apply Conditional Formatting to other workbooks. Can you bring the data into the same workbook? Just move to a separate sheet / hide if necessary?