Something like SetBinContent but cumulative

Hi all,

Is there any possibility to do something like SetBinContent but on a
cumulative way? I mean, that I did SetBinContent on a bin, and I
would like to do it again, and not setting the bin content new, but
adding some value to that bins content again.
For example, something like:
Int_t bin = 5;
histo->SumBinContent(bin, 0.78);
and then
histo->SumBinContent(bin, 1.03);
and after that, the content of the bin no. 5 would be 1.81
I would need this, because I do not want to put the former bin
contents in the memory.
I know, it is possible to do it on some roundabout ways, but there is
maybe a possibility in root to do that without any tricks.

Mate Csanad

see TH1::AddBinContent