Thank you Thomas for this very complete and detail answer, I will try it as soon as possible, like the scripting method. 

I found an alternative before the weekend (a good time to launch several calculations): I create as many copies of mechanical parts as necessary, and I apply to each one a material to test; ditto for the sources if I want to calculate with several sources. 
"I only have" (the most difficult and long part) to create as many simulations as necessary, selecting the right geometries and the right sources. 

Effectively, the best would be that I master the scripts.