Conditional formatting based on two cell values

Hi and welcome to the forum

If R is =TEXT(M4-H4,"h:mm:ss"), then this is text, and you cannot perform math functions on text What I would suggest is to use the actual formula inside there (=M4-H4) in your CF rule

Perhaps it would be easier to offer a better suggestion is you provided a sample workbook with dummy data, showing a few samples of your expected outcome?
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Thanks for the file.

1st, unless you have a specific reason for needing the calc in E to be text, you can just use =D2-B2 copied down (format as needed, although excel will probably format it correctly for you.

2nd, try this formula in your CF rule...
1. highlight the range you want to apply the conditional formatting to
2. on the home tab, styles, select CF
3. select new rule, select use formula
4. enter =OR(AND(C2="P3",E2>30/60/24),AND(C2="P2",E2>10/60/24))

Check what you did. When I used that, it high-lighted E10 and E12 red.

Follow my instructions for applying the CF rule

Yes, when you format under CF, click the "FILL" tab and you can specify colors there