Compare cell values and display negative or positive value?

[Lika]

New to LibreOffice calc and its a big program =).
Lets imagine I have cells looking like this below. In C column I want to add values of difference from previous value in B column

A                 B         C
2019-01-02       500
2019-01-03       700
2019-01-04       200
2019-01-05       800

So it look s something like this -

A                 B         C
2019-01-02       500   
2019-01-03       700       200
2019-01-04       200      -500
2019-01-05       800       600

How to achive this the smartest way?

[Hrbrgr]

If my answer did solve your problem, please click the big checkmark inside the circle to the left of this answer. It then indicates to the other participants that the question has been answered correctly.

[Hrbrgr]

With me Windows 10 Home; Version 1809; 64-Bit | LibreOffice, Version: 6.2.4.2 (x64)…

[Lika]

With greatest gratitude I thank you´for your answer and helping me out.
Danke Schön!

[Hrbrgr]

Always my pleasure.