Calculating differences for different companies under each other

Hi,

I'm writing my thesis and I have a bunch of data about listed companies.

Attachment 781333

The data consists of quarterly leverage ratios (LV ratio). I want to calculate the change in leverage ratio (LV change). To do this, I subtract each cell with the cell above it. In the example, you can see two different companies, ASM and British American Tobacco. I do not want to subtract the leverage ratio of British American Tobacco with the ASM's one (Row 85). Is there a way to tell Excel to only subtract the values of a certain company with each other and do this for every company separately? I can't do it manually because I have 29.000 rows.

I found it difficult to explain it so I hope it's clear enough.

Thanks