Role histogramme to show split project code grouping Primavera P6 v6.2

Hi,

Have assigned 1 role to not started/in progress construction activity for histogramme show monthly men requirement.

role_histogramme.jpg

Have now been asked to show same on 1 histogramme but  split per operational area (S, N, W, E) which is a project code e.g  stacked histogramme to show that in January 2013, 2 men required in N, 1 in S, 2 in W and 5 in E.

Not been able to do so, only way I can think is to group projects on operational area and issue 1 histogramme for each of them.

Any ideas?

Thanks.

E.