Calculating differences between cell contents 'by blocks'

[TF1985]

Hello everyone,

I have a little problem with a macro somebody here might be able to help me with. Unfortunately the upload function doesn't seem to work for me so I'll have to describe the sheet. It looks something like this (I hope it's understandable, column C is empty here):
A B C
1 68
1 72
1 85
1 91
1 102
2 40
2 54
2 60
2 68
3 76
3 86
3 94

So in column A I have the number of the corresponding 'block' of data, which is ascending by one (it's around 400 in the original file, I just put 1-3 here for this example). In column B I have corresponding data which is always rising from one cell to the next, until the next block starts (e.g 1 -> 2). The length of these blocks varies.

Now in column C, what I would like to do is calculate a list of the differences of those numbers in column B in regards to the FIRST entry of that block (which would itself be changed to "0"). So in this example the outcome should look something like this:

A B C
1 68 0
1 72 4
1 85 17
1 91 23
1 102 34
2 40 0
2 54 14
2 60 20
2 68 etc.
3 76
3 86
3 94

I hope you guys can understand what I mean I'm really new to VBA and I'm having trouble figuring this out, especially how I should program the macro so that it starts from zero again once the block changes (when the number in column A increases by one).

Any help would be greatly appreciated! Thank you.

[6StringJazzer]

If you put this formula in C1 and copy down for all data then you don't need VBA. I tested this out on your sample data.

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If for some reason you still need macros, come back, we can do that too.

[TF1985]

Hey, thank you!

But somehow this produces an error message in my case? :/

[oeldere]

You don't need VBA for that.

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See the yellow cells in the attached example.

[TF1985]

Works like a charm! You just saved me from a lot of troubles

THANKS to both of you!

[6StringJazzer]

Glad you got something to work but I'm puzzled by your reference to an error message. What error? Here is my implementation using your sample data: [TF1985=series of blocks.xlsx]

[TF1985]

Ah it was just that I put it in exactly like the quote above, and there the arguments are separated by commas, as opposed to semicolons. It works perfectly of course in your sample. As I said I'm new to Excel, could have figured that out myself

Thanks again.

[6StringJazzer]

I see. I am using the U.S. settings and I think European settings use the semi-colon. I wrote my formula with commas in my file but when you open, I guess you see semi-colons.

[TF1985]

Ah okay, yeah that's probably the explanation - I see semicolons