Oh, i see.. the array was the solution.
I'm so dumb.. i use array for all my "gauge" like "chronograph" but I didnt use them for this case..

First I thought it couldnt work because i needed to do the same thing with
ja1.visible=on;ja2.visible=on;ja3.visible=on;ja10.visible=on; and I think its not that simple in this case, but this is another problem.
I hope i will find a solution with that way.

edit : looks unaccessible with strings instead of variables

Anyway, i'll try it right now and i guess there will be no problem.
Thanks for your 2 answers and for the detailed code and the tip.