Formula to identify variance

I have a report where I am looking at weekly volumes. The ask for his report is to provide some sort of visual identification to highlight when one weeks volume may seem abnormally higher or lower than the previous week. I've attached an example with 13 weeks of data. If you look at the first week it's at 497 while the rest of the weeks are pretty much around 700. I would want a way to highlight that cell as a callout, maybe in yellow.

Is there a formula that I could apply that compares week over week and determines if it is plus/minus a certain percentage of the cell next to it that it would highlight it? I know that is pretty vague but I want to leave it high level to start.

Also, there would be about 3,000 rows of data that I would have to apply this to.

Thanks in advanced guys! If you need me to clarify more please let me know.

Thanks,
Bob

Jeff,

Thanks a lot for the quick response. I figured it was something to do with Conditional Formatting I just wasn't very sure on the formula. What you wrote made sense. Thank you for offering to work on the file, unfortunately it is confidential based on the client related data.

I will try your solution tomorrow at work and will report back either way.

Thanks again and have a great night!

Bob