Alright I found the answer myself (one more time 
)
The reason it did not work was because the variable is well set by the “set float/int by name”… but … the actor was not updated because it was set by the construction script before the variable was set by an other actor event.
I could figure out the variable was well set by adding a “get float by name” after a “set float by name”.
Then I had to find a way to force the actor to update. An easy way I found is to toggle its visibility twice… (May be there is an other way with 1 single node?).
Btw it works well now 