Thanks Paul for your attention to this topic. As far as I understand I can use the actual Dload pressure system witch already balances forces on nodes accordingly to the surface of mesh faces.
Then I need to weigh the pressure with a factor = rho*G*H accordindly to the altitude of each face of mesh from the initial surface witch is the height reference.
If this strategie involves to deal with C language I think I will fail because of my lack of skills.
As Bernd said, maybe a macro would be easier and faster to developpe , furthermore suitable with my very limited skills in programing.
I have to read and learn a lot before to ask more questions and advices. Now I'm not at home and I access the forum with smartphone so it's not convenient to make some progress.
To be continues...
Any advice and opinion still appreciated