Hi franz,
If you know the total number of samples, say 1234, then you can set the "Divided by Factor" option 
in Tick Labels tab for the Y Axis dialog box:1234/100
If you don't have this number, 
you can first run the following commands in the Script window:range rr=[Book1]!col(B);
sum(rr);
n1=sum.n;
Then, enter the following to the "Divided by Factor" option :n1/100
I hope this helps.
--Hideo Fujii
OriginLab
postscript: 
1) The sample size by the second method excludes the missing values or text values. To make sure 
the number of samples, this would be helpful rather than just look at the row# of the bottom cell.
2) Here, "n1" is a global(project) variable, so it is saved within the project, and it is 
always available when you open the project file. However, if you make more than one histogram, 
you should use other variable names to avoid the conflict.