Simple SUMIF formula performance problems in macro

[rpinxt]

Dear all,

I have some code which copies down a cell in which a SUMIF formula calculates something for me.
And this is really somehow bad on the performance of the macro although it is a really really simple SUMIF.
Ok there are over 20000 lines but still....

I have attached a workbook with the 3 columns in scope.
C2 is the cell that contains the formula.
In fact you can even try to copy down the formula in "normal" excel so without VBA and it still is very very slow.
My laptop at work has 4GB RAM and 4 core processor and all 4 cores are being used, so I don't think it is the hardware.

So is this just how it is or can something be altered in the coding or setting by which it runs faster?
Thanks.

[rpinxt]

I take everybody has this performance problem when using sumif on a large sets op lines??