Need SAP BI report with function to find VIN with tampered odometer mileage

I want to build a SAP BI document where I process a lots of vehicle data in order to find vehicles with tampered mileage odometer. The data table include VIN, and Date / Mileage at each service visit.

I am absolutely a beginner and need help with some simple coding, how to set up the variables in SAP BI 4.2 Web interface, so the report can process and find the VINs with manipulated mileage odometer.

Normally the mileage increase when the car is used. I want to find these VIN's where mileage has decreased with previous date.

The example show 2 VIN's which one have a tampered mileage.

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